Update playwright version

Reviewed-on: #4

.claude/settings.local.json

@@ -0,0 +1,9 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(npm test:*)",
+      "Bash(npm run:*)",
+      "Bash(npx playwright:*)"
+    ]
+  }
+}

.gitea/workflows/test.yml

@@ -0,0 +1,55 @@
+name: Tests
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  backend-test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Use Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '24'
+          # cache: ''npm''
+          # cache-dependency-path: backend/package-lock.json
+      - name: Install dependencies
+        run: cd backend && npm ci
+      - name: Run tests
+        run: cd backend && npm test
+
+  frontend-test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Use Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '24'
+          # cache: 'npm'
+          # cache-dependency-path: frontend/package-lock.json
+      - name: Install dependencies
+        run: cd frontend && npm ci
+      - name: Run unit tests
+        run: cd frontend && npm test -- --run
+
+  e2e-test:
+    runs-on: ubuntu-latest
+    container:
+      image: mcr.microsoft.com/playwright:v1.58.2-noble
+    steps:
+      - uses: actions/checkout@v4
+      - name: Use Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '24'
+          # cache: 'npm'
+          # cache-dependency-path: frontend/package-lock.json
+      - name: Install dependencies
+        run: cd frontend && npm install
+      - name: Run E2E tests
+        run: cd frontend && npm run test:e2e

.github/copilot-instructions.md

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+# Copilot Instructions for line-of-sight
+
+## Purpose
+This repository is a full-stack geospatial app:
+- `frontend/`: React + Vite + MapLibre UI
+- `backend/`: Express API with PostGIS queries
+- `docker/` and `docker-compose.yml`: local orchestration and DB initialization
+
+Prefer small, focused changes that keep frontend/backend contracts stable.
+
+## First Commands to Know
+Use these commands first when validating changes.
+
+### Docker-first workflow (preferred)
+- Start stack: `docker-compose up --build`
+- Stop stack: `docker-compose down`
+- Backend tests: `docker-compose exec backend npm test`
+- Frontend unit tests: `docker-compose exec frontend npm test -- --run`
+- Frontend E2E tests: `docker-compose exec frontend npm run test:e2e`
+- Seed geodata: `docker-compose exec backend npm run seed-data`
+
+### Local workflow (without Docker)
+- Root Node version: `nvm use` (uses `.nvmrc`, currently Node 24)
+- Backend dev: `cd backend && npm install && npm run dev`
+- Frontend dev: `cd frontend && npm install && npm run start`
+
+## Architecture and Boundaries
+- Backend API entrypoint: `backend/app/server.js`
+  - Defines `GET /api/line-of-sight` and `GET /api/health`
+  - Performs destination/path generation and PostGIS querying
+- Frontend app entrypoint: `frontend/src/App.jsx`
+  - Owns map lifecycle, animation, and UI state
+  - Calls backend via `frontend/src/services/api.js`
+- Database bootstrap: `docker/init.sql`
+  - Enables PostGIS and creates `cities` with spatial index
+
+When changing behavior, prefer backend geospatial logic over duplicating calculations in the frontend.
+
+## Project Conventions
+- Keep geospatial coordinates in WGS84 (`SRID 4326`) and preserve existing lat/lon parameter naming.
+- Keep API responses JSON-compatible and backward compatible unless explicitly requested.
+- Keep frontend styles in `frontend/src/styles/` (project uses custom CSS, not utility CSS frameworks).
+- Avoid broad refactors in `App.jsx` unless task requires it; map lifecycle and refs are tightly coupled.
+
+## Testing Expectations
+- Backend tests live in `backend/tests/` and use Jest + Supertest.
+- Frontend unit tests live in `frontend/src/__tests__/` and use Vitest + Testing Library.
+- E2E tests live in `frontend/e2e/` and use Playwright.
+- For feature changes:
+  - Run the closest unit tests first.
+  - Run E2E tests when user flows or map interactions are changed.
+
+## Common Pitfalls
+- PostGIS must be available before backend geospatial endpoints are exercised.
+- `docker-compose.yml` pins Postgres service to `linux/arm64`; this can affect non-ARM hosts.
+- Data import script (`backend/scripts/import_cities.js`) depends on `wget` and `unzip` availability.
+- `README.md` contains roadmap/history notes; trust current scripts/config in source files first.
+
+## CI Notes
+CI config is in `.gitea/workflows/test.yml`.
+- Backend and frontend tests run on Node 24.
+- Frontend unit tests run with `npm test -- --run`.
+- E2E runs in Playwright container.
+
+## Link, Do Not Duplicate
+For detailed setup and product context, reference:
+- `README.md`
+- `GEMINI.md`
+
+Keep this file focused on actionable agent guidance and repo-specific guardrails.

.nvmrc

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+24

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## What This Project Is
+
+**Line of Sight** is a geospatial web app that draws a great-circle line from a user-selected point on Earth in a chosen direction, then finds all cities along that path. It includes a flight-over animation that speeds up 20x over water and slows to normal speed over land.
+
+## Commands
+
+### Docker (preferred workflow)
+
+```bash
+docker-compose up --build       # Start all services (frontend :3050, backend :3001, postgres)
+docker-compose down             # Stop all services
+docker-compose logs -f          # View logs
+
+# Run tests inside containers
+docker-compose exec backend npm test
+docker-compose exec frontend npm test -- --run
+docker-compose exec frontend npm run test:e2e
+```
+
+### Local development (without Docker)
+
+```bash
+# Backend
+cd backend && npm run dev       # Nodemon dev server on :3001
+
+# Frontend
+cd frontend && npm run start    # Vite dev server on :3050
+```
+
+### Tests
+
+```bash
+# Backend unit tests (Jest + Supertest)
+cd backend && npm test
+
+# Frontend unit tests (Vitest)
+cd frontend && npm test          # Watch mode
+cd frontend && npm test -- --run # Single run (CI mode)
+
+# E2E tests (Playwright)
+cd frontend && npm run test:e2e
+
+# Seed the database with GeoNames city data
+cd backend && npm run seed-data
+```
+
+### Build
+
+```bash
+cd frontend && npm run build    # Vite production build → frontend/build/
+```
+
+## Architecture
+
+This is a monorepo with three services orchestrated by Docker Compose:
+
+```
+frontend/  → React 19 + Vite 6 SPA (MapLibre GL, Turf.js, Axios)
+backend/   → Node 24 + Express 5 REST API
+docker/    → PostgreSQL + PostGIS initialization
+```
+
+### Data flow
+
+1. User clicks map → sets start point (lat/lon)
+2. User selects direction (0–360°) and tolerance (km radius)
+3. Frontend calls `GET /api/line-of-sight?lat=&lon=&direction=&tolerance=`
+4. Backend generates 80 path points along a great-circle arc (up to 20,000 km)
+5. For each point, a PostGIS `ST_DWithin()` query finds cities within tolerance
+6. Backend also checks whether each point is over land (500 km radius land check)
+7. Response includes line coordinates with per-point water flags and matching cities
+8. Frontend renders the path on a 3D globe map and shows city markers
+
+### Backend: `backend/app/server.js`
+
+Single-file Express app. Key internals:
+- `calculateDestination()` — Haversine formula for great-circle destination points
+- `GET /api/line-of-sight` — main endpoint: path generation + PostGIS city lookup
+- `GET /api/health` — health check
+- Returns up to 200 cities ordered by position along the line
+
+### Frontend: `frontend/src/App.jsx`
+
+Single large React component (~687 lines) managing all state and map logic:
+- MapLibre GL map with 3D globe projection and terrain/sky effects
+- Direction slider drives a live preview line before the user commits
+- After "Show Line of Sight", map locks (prevents moving start point)
+- Flight animation uses Turf.js to interpolate positions along the path; speed is 1× over land, 20× over water with smooth acceleration (0.005 step), predictive look-ahead of 2000 km
+- New cities are fetched every 2000 km during flight via the same API
+- Three map styles: light, dark, satellite (Esri tiles)
+
+### Database
+
+PostGIS `cities` table with a GIST index on `geom GEOGRAPHY(POINT, 4326)`. All coordinates use WGS84 / SRID 4326. The init SQL seeds 10 major cities; the `seed-data` script imports from GeoNames for a fuller dataset.
+
+## Conventions
+
+- **Geospatial**: WGS84 / SRID 4326 everywhere; PostGIS `GEOGRAPHY` type for distance queries
+- **API**: RESTful; query params for `GET /api/line-of-sight`; env var `VITE_API_URL` (frontend) or `DATABASE_URL` (backend)
+- **Styling**: Plain CSS files in `frontend/src/styles/` — no CSS framework
+- **Tests**: Backend mocks the `pg` Pool; frontend mocks MapLibre GL and the API service. E2E tests use Playwright with a mock API response
+
+## CI
+
+Gitea workflow (`.gitea/workflows/test.yml`) runs on push/PR to `main`:
+1. **backend-test** — `npm ci && npm test`
+2. **frontend-test** — `npm ci && npm test -- --run`
+3. **e2e-test** — uses `mcr.microsoft.com/playwright:v1.50.1` container

GEMINI.md

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+# GEMINI.md - Project Context: Line of Sight 🌍
+
+## 🚀 Project Overview
+**Line of Sight** is an interactive web application that visualizes great-circle paths around the Earth and identifies major conurbations (cities) along those paths based on user-defined direction and "fuzziness" tolerance.
+
+### Architecture
+- **Frontend**: React 19 single-page application using Vite 6 for build orchestration and MapLibre GL JS for vector map rendering.
+- **Backend**: Node.js 24/Express 5 REST API.
+- **Database**: PostgreSQL with the PostGIS extension for geospatial data storage and analysis. Uses `kartoza/postgis` for robust multi-arch (including ARM64) support.
+- **Infrastructure**: Fully containerized using Docker and orchestrated with Docker Compose.
+
+---
+
+## 🛠️ Tech Stack
+- **Frontend**: `React 19`, `Vite 6`, `MapLibre GL JS`, `Axios`
+- **Backend**: `Node.js 24`, `Express 5`, `node-postgres (pg) 8.20`
+- **Database**: `PostgreSQL (kartoza/postgis)`, `PostGIS`
+- **Testing**: `Vitest` (Frontend), `Jest` (Backend)
+- **DevOps**: `Docker`, `Docker Compose`
+
+---
+
+## 🚦 Getting Started & Key Commands
+
+### Complete System (Docker)
+| Action | Command |
+| :--- | :--- |
+| **Start Services** | `docker-compose up` |
+| **Rebuild & Start** | `docker-compose up --build` |
+| **Stop Services** | `docker-compose down` |
+| **View Logs** | `docker-compose logs -f` |
+| **Access DB (psql)** | `docker-compose exec postgres psql -U line_of_sight -d line_of_sight` |
+
+### Backend Development (`/backend`)
+| Action | Command |
+| :--- | :--- |
+| **Install** | `npm install` |
+| **Start (Prod)** | `npm start` |
+| **Start (Dev)** | `npm run dev` (Uses nodemon) |
+| **Test** | `npm test` |
+
+### Frontend Development (`/frontend`)
+| Action | Command |
+| :--- | :--- |
+| **Install** | `npm install` |
+| **Start (Dev)** | `npm run start` (Starts Vite) |
+| **Build** | `npm run build` |
+| **Test** | `npm run test` (Starts Vitest) |
+
+---
+
+## 📁 Key File Map
+- `backend/app/server.js`: Main Express entry point and API route definitions.
+- `frontend/src/App.js`: Primary React component containing map logic and state management.
+- `frontend/src/services/api.js`: Axios-based API client for backend communication.
+- `docker/init.sql`: Database schema definition including PostGIS extension and seed data.
+- `docker-compose.yml`: Service orchestration for the entire stack.
+
+---
+
+## 🔧 Development Conventions
+- **Node Versioning**: Use `nvm` to manage Node.js. Run `nvm use` in the root directory to switch to Node 24 (specified in `.nvmrc`).
+- **Geospatial Standards**: Latitude/Longitude are handled in decimal degrees. Geometry uses `SRID 4326` (WGS 84).
+- **API Design**: RESTful endpoints returning JSON. The primary endpoint is `GET /api/line-of-sight`.
+- **Styling**: Prefer custom CSS in `frontend/src/styles/` over utility-first frameworks like Tailwind for this specific project.
+- **Testing**: Tests are located in `backend/tests/` and `frontend/src/__tests__/`. Use `vitest` (Frontend) and `jest` (Backend).
+- **Environment**: Use `.env` files for configuration. `VITE_API_URL` is required for the frontend.
+
+---
+
+## 📝 Roadmap Highlights
+- [ ] Implement real ST_DWithin() PostGIS queries in the backend.
+- [ ] Import full Natural Earth/GeoNames datasets into the `cities` table.
+- [ ] Transition from 2D MapLibre to a 3D globe visualization.
+- [ ] Optimize line-of-sight calculations for long-distance paths.

README.md

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+# Line of Sight 🌍
+
+Interactive web application that visualizes lines of sight around the Earth, showing major conurbations along any selected path.
+
+## 🚀 Features
+
+- **Interactive Map**: Click anywhere to select starting coordinates
+- **360° Direction Selector**: Choose any direction with compass-style control
+- **Fuzziness Tolerance**: Adjustable search radius around the line of sight
+- **Tube-Line Visualization**: Shows up to 20 major cities along the path
+- **Real-time Rendering**: Instant feedback on map with city markers
+- **Map Style Toggle**: Switch between light and dark themes
+
+## 🛠️ Tech Stack
+
+### Frontend
+- **Framework**: React 18
+- **Map Library**: MapLibre GL JS
+- **HTTP Client**: Axios
+- **Styling**: Custom CSS
+
+### Backend
+- **Runtime**: Node.js 18
+- **Framework**: Express.js
+- **Database**: PostgreSQL 15 with PostGIS 3.3
+
+### DevOps
+- **Containerization**: Docker + Docker Compose
+- **Database**: PostGIS spatial extension
+
+## 📋 Prerequisites
+
+- Docker 20.10+
+- Docker Compose 2.0+
+- Git (for repository access)
+
+## 🚦 Getting Started
+
+### 1. Clone Repository
+
+```bash
+git clone https://repos.retroweb.dev/ai-zone/line-of-sight.git
+cd line-of-sight
+```
+
+### 2. Run with Docker
+
+```bash
+docker-compose up --build
+```
+
+### 3. Access Application
+
+- **Frontend**: http://localhost:3050
+- **Backend API**: http://localhost:3001
+- **Database**: localhost:5432 (PostgreSQL with PostGIS)
+
+## 🎮 How to Use
+
+1. **Select Point**: Click anywhere on the map to set your starting coordinate
+2. **Set Direction**: Use the slider to choose 0-360° direction
+3. **Adjust Tolerance**: Set fuzziness (how close cities must be to the line)
+4. **Show Line of Sight**: Click the button to visualize the path
+5. **View Results**: See up to 20 major conurbations along the path
+
+## 🧪 Running Tests
+
+### Backend Tests
+```bash
+docker-compose exec backend npm test
+```
+
+### Frontend Tests
+```bash
+docker-compose exec frontend npm test
+```
+
+## 📡 API Endpoints
+
+### GET /api/line-of-sight
+Returns conurbations along a line of sight.
+
+**Parameters:**
+- `lat` (float): Starting latitude
+- `lon` (float): Starting longitude
+- `direction` (int): Direction in degrees (0-360)
+- `tolerance` (int): Fuzziness tolerance in km (default: 50)
+
+**Response:**
+```json
+{
+  "success": true,
+  "data": {
+    "start_point": { "lat": 51.5074, "lon": -0.1278 },
+    "direction": 45,
+    "tolerance_km": 50,
+    "conurbations": [...],
+    "line_coordinates": [...]
+  }
+}
+```
+
+### GET /api/health
+Health check endpoint.
+
+## 🐳 Docker Commands
+
+### Start Services
+```bash
+docker-compose up
+```
+
+### Start in Background
+```bash
+docker-compose up -d
+```
+
+### Stop Services
+```bash
+docker-compose down
+```
+
+### Rebuild and Start
+```bash
+docker-compose up --build
+```
+
+### View Logs
+```bash
+docker-compose logs -f
+```
+
+### Access Database
+```bash
+docker-compose exec postgres psql -U line_of_sight -d line_of_sight
+```
+
+## 📁 Project Structure
+
+```
+line_of_sight/
+├── backend/
+│   ├── app/
+│   │   └── server.js          # Express API server
+│   ├── tests/                 # Backend tests
+│   ├── Dockerfile
+│   └── package.json
+├── frontend/
+│   ├── src/
+│   │   ├── App.js            # Main React component
+│   │   ├── services/         # API client
+│   │   └── styles/           # CSS files
+│   ├── public/
+│   ├── Dockerfile
+│   └── package.json
+├── docker/
+│   └── init.sql              # Database initialization
+├── docker-compose.yml        # Container orchestration
+├── README.md                 # This file
+└── .gitignore
+```
+
+## 🧩 Development
+
+### Frontend Development
+```bash
+cd frontend
+npm install
+npm start
+```
+
+### Backend Development
+```bash
+cd backend
+npm install
+npm run dev
+```
+
+## 📝 Current Status
+
+**MVP Version 1.0**
+
+- ✅ Interactive map with coordinate selection
+- ✅ Direction selector (0-360°)
+- ✅ Fuzziness tolerance control
+- ✅ Mock API returning 20 conurbations
+- ✅ Line visualization on map
+- ✅ City markers with popup info
+- ⏳ Real geospatial calculations (Phase 2)
+- ⏳ Natural Earth data import (Phase 2)
+- ⏳ GeoNames integration (Phase 3)
+
+## 🔮 Roadmap
+
+### Phase 1: MVP ✅
+- Basic map interface
+- Dummy API endpoints
+- Docker containerization
+
+### Phase 2: Real Geospatial
+- Great circle calculations
+- PostGIS queries with ST_DWithin()
+- Natural Earth data import
+
+### Phase 3: Enhanced Features
+- GeoNames dataset integration
+- 3D globe visualization
+- Distance calculations
+- Performance optimization
+
+### Phase 4: Production Ready
+- User authentication
+- Saved searches
+- Export functionality
+- Mobile optimization
+
+## 🐛 Troubleshooting
+
+### Port Already in Use
+```bash
+# Find process using port
+lsof -i :3050
+lsof -i :3001
+
+# Kill process
+kill -9 <PID>
+```
+
+### Database Connection Issues
+```bash
+# Check if database is running
+docker-compose ps
+
+# Restart database
+docker-compose restart postgres
+```
+
+### Build Issues
+```bash
+# Clean and rebuild
+docker-compose down
+docker-compose build --no-cache
+docker-compose up
+```
+
+## 🤝 Contributing
+
+1. Create a feature branch
+2. Make your changes
+3. Add tests for new functionality
+4. Ensure all tests pass
+5. Submit a Pull Request
+
+## 📄 License
+
+MIT License
+
+## 📞 Support
+
+For issues or questions, please open an issue on the repository.
+
+---
+
+*Built with ❤️ by Agent Zero*

backend/Dockerfile

@@ -1,4 +1,4 @@
-FROM node:18-alpine
+FROM node:24-alpine
 
 WORKDIR /app
 

backend/app/server.js

@@ -1,66 +1,130 @@
 const express = require('express');
 const cors = require('cors');
+const { Pool } = require('pg');
 require('dotenv').config();
 
 const app = express();
 const PORT = process.env.PORT || 3001;
 
+// Database connection pool
+const pool = new Pool({
+  connectionString: process.env.DATABASE_URL || 'postgresql://line_of_sight:line_of_sight_pass@postgres:5432/line_of_sight'
+});
+
 app.use(cors());
 app.use(express.json());
 
-// Mock conurbation data for MVP
+// Helper to calculate destination point given start, bearing, and distance (km)
-const MOCK_CONURBATIONS = [
+const calculateDestination = (lat, lon, bearing, distance) => {
-  { id: 1, name: "London", population: 9000000, distance_km: 0, lat: 51.5074, lon: -0.1278 },
+  const R = 6371;
-  { id: 2, name: "Paris", population: 2161000, distance_km: 344, lat: 48.8566, lon: 2.3522 },
+  const brng = (bearing * Math.PI) / 180;
-  { id: 3, name: "Berlin", population: 3644000, distance_km: 878, lat: 52.5200, lon: 13.4050 },
+  const φ1 = (lat * Math.PI) / 180;
-  { id: 4, name: "Warsaw", population: 1793000, distance_km: 1200, lat: 52.2297, lon: 21.0122 },
+  const λ1 = (lon * Math.PI) / 180;
-  { id: 5, name: "Moscow", population: 12506000, distance_km: 2063, lat: 55.7558, lon: 37.6173 },
+  const δ = distance / R;
-  { id: 6, name: "Kazan", population: 1257000, distance_km: 2850, lat: 55.7897, lon: 49.1219 },
-  { id: 7, name: "Almaty", population: 2000000, distance_km: 3900, lat: 43.2220, lon: 76.8512 },
-  { id: 8, name: "Urumqi", population: 3500000, distance_km: 4500, lat: 43.8256, lon: 87.6168 },
-  { id: 9, name: "Lahore", population: 11126000, distance_km: 5400, lat: 31.5204, lon: 74.3587 },
-  { id: 10, name: "New Delhi", population: 29399000, distance_km: 5800, lat: 28.6139, lon: 77.2090 },
-  { id: 11, name: "Dhaka", population: 21006000, distance_km: 6200, lat: 23.8103, lon: 90.4125 },
-  { id: 12, name: "Chennai", population: 10971000, distance_km: 6500, lat: 13.0827, lon: 80.2707 },
-  { id: 13, name: "Bangkok", population: 10539000, distance_km: 7200, lat: 13.7563, lon: 100.5018 },
-  { id: 14, name: "Jakarta", population: 10562000, distance_km: 8100, lat: -6.2088, lon: 106.8456 },
-  { id: 15, name: "Singapore", population: 5686000, distance_km: 8300, lat: 1.3521, lon: 103.8198 },
-  { id: 16, name: "Manila", population: 17801000, distance_km: 8700, lat: 14.5995, lon: 120.9842 },
-  { id: 17, name: "Tokyo", population: 37400000, distance_km: 9500, lat: 35.6762, lon: 139.6503 },
-  { id: 18, name: "Seoul", population: 9720000, distance_km: 9200, lat: 37.5665, lon: 126.9780 },
-  { id: 19, name: "Beijing", population: 21540000, distance_km: 8900, lat: 39.9042, lon: 116.4074 },
-  { id: 20, name: "Shanghai", population: 27058000, distance_km: 9000, lat: 31.2304, lon: 121.4737 }
-];
 
-// Mock API endpoint - returns dummy conurbations based on input coordinates
+  const φ2 = Math.asin(
-app.get('/api/line-of-sight', (req, res) => {
+    Math.sin(φ1) * Math.cos(δ) +
+      Math.cos(φ1) * Math.sin(δ) * Math.cos(brng)
+  );
+  const λ2 =
+    λ1 +
+    Math.atan2(
+      Math.sin(brng) * Math.sin(δ) * Math.cos(φ1),
+      Math.cos(δ) - Math.sin(φ1) * Math.sin(φ2)
+    );
+
+  return {
+    lat: (φ2 * 180) / Math.PI,
+    lon: (((λ2 * 180) / Math.PI + 540) % 360) - 180
+  };
+};
+
+// Real API endpoint - uses PostGIS for spatial queries
+app.get('/api/line-of-sight', async (req, res) => {
   const { lat, lon, direction, tolerance } = req.query;
   
-  console.log(`Received request: lat=${lat}, lon=${lon}, direction=${direction}, tolerance=${tolerance}`);
+  const startLat = parseFloat(lat) || 51.5074;
-  
+  const startLon = parseFloat(lon) || -0.1278;
-  // Return mock data for MVP
+  const bearing = parseInt(direction) || 0;
-  res.json({
+  const toleranceKm = parseInt(tolerance) || 50;
-    success: true,
+
-    data: {
+  console.log(`Processing real request: lat=${startLat}, lon=${startLon}, bearing=${bearing}, tolerance=${toleranceKm}`);
-      start_point: { lat: parseFloat(lat) || 51.5074, lon: parseFloat(lon) || -0.1278 },
+
-      direction: parseInt(direction) || 45,
+  try {
-      tolerance_km: parseInt(tolerance) || 50,
+    // Generate path points for visualization and spatial query
-      conurbations: MOCK_CONURBATIONS.slice(0, 20),
+    const pathPoints = [];
-      line_coordinates: [
+    const totalDistance = 20000;
-        { lat: 51.5074, lon: -0.1278 },
+    const steps = 80; // More steps for smoother speed transition
-        { lat: 48.8566, lon: 2.3522 },
+    
-        { lat: 52.5200, lon: 13.4050 },
+    for (let i = 0; i <= steps; i++) {
-        { lat: 55.7558, lon: 37.6173 },
+      const dist = (totalDistance * i) / steps;
-        { lat: 43.2220, lon: 76.8512 },
+      pathPoints.push(calculateDestination(startLat, startLon, bearing, dist));
-        { lat: 28.6139, lon: 77.2090 },
+    }
-        { lat: 13.7563, lon: 100.5018 },
+
-        { lat: -6.2088, lon: 106.8456 },
+    // Batch check for 'over water' status for all path points
-        { lat: 35.6762, lon: 139.6503 },
+    // We'll consider a point 'over water' if no city is within 500km
-        { lat: 51.5074, lon: -0.1278 } // Complete the circle
+    const waterChecks = await Promise.all(pathPoints.map(async (p) => {
-      ]
+      const checkQuery = `
-    },
+        SELECT EXISTS (
-    message: "Mock data returned for MVP - Real geospatial calculations coming soon"
+          SELECT 1 FROM cities 
-  });
+          WHERE ST_DWithin(geom, ST_SetSRID(ST_MakePoint($1, $2), 4326)::geography, 500000)
+          LIMIT 1
+        ) as has_land;
+      `;
+      const res = await pool.query(checkQuery, [p.lon, p.lat]);
+      return !res.rows[0].has_land;
+    }));
+
+    const pathPointsWithWater = pathPoints.map((p, i) => ({
+      ...p,
+      is_over_water: waterChecks[i]
+    }));
+
+    const lineWKT = `LINESTRING(${pathPoints.map(p => `${p.lon} ${p.lat}`).join(',')})`;
+    
+    const query = `
+      WITH path AS (
+        SELECT ST_GeogFromText($1) as route,
+               ST_MakePoint($3, $4)::geography as start_node
+      )
+      SELECT 
+        id, 
+        name, 
+        population, 
+        country,
+        ST_Y(geom::geometry) as lat, 
+        ST_X(geom::geometry) as lon,
+        ST_Distance(geom, (SELECT route FROM path)) / 1000 as distance_off_line_km,
+        ST_Distance(geom, (SELECT start_node FROM path)) / 1000 as distance_from_start_km,
+        ST_LineLocatePoint((SELECT route FROM path)::geometry, geom::geometry) as pos_on_line
+      FROM cities
+      WHERE ST_DWithin(geom, (SELECT route FROM path), $2 * 1000)
+      ORDER BY pos_on_line ASC
+      LIMIT 200;
+    `;
+
+    const result = await pool.query(query, [lineWKT, toleranceKm, startLon, startLat]);
+    
+    res.json({
+      success: true,
+      data: {
+        start_point: { lat: startLat, lon: startLon },
+        direction: bearing,
+        tolerance_km: toleranceKm,
+        conurbations: result.rows.map(row => ({
+          ...row,
+          name: row.name || 'Unknown',
+          country: row.country || 'Unknown',
+          distance_km: Math.round(row.distance_from_start_km),
+          off_line_km: Math.round(row.distance_off_line_km)
+        })),
+        line_coordinates: pathPointsWithWater
+      }
+    });
+  } catch (err) {
+    console.error('Database query error:', err);
+    res.status(500).json({ success: false, error: 'Database query failed' });
+  }
 });
 
 // Health check endpoint
@@ -68,6 +132,10 @@ app.get('/api/health', (req, res) => {
   res.json({ status: 'ok', timestamp: new Date().toISOString() });
 });
 
-app.listen(PORT, '0.0.0.0', () => {
+if (require.main === module) {
-  console.log(`Line of Sight Backend running on port ${PORT}`);
+  app.listen(PORT, '0.0.0.0', () => {
-});
+    console.log(`Line of Sight Backend running on port ${PORT}`);
+  });
+}
+
+module.exports = { app, calculateDestination };

backend/package.json

@@ -6,16 +6,19 @@
   "scripts": {
     "start": "node app/server.js",
     "dev": "nodemon app/server.js",
-    "test": "jest"
+    "test": "jest",
+    "seed-data": "node scripts/import_cities.js"
   },
   "dependencies": {
-    "express": "^4.18.2",
+    "axios": "^1.13.6",
-    "cors": "^2.8.5",
+    "cors": "^2.8.6",
-    "pg": "^8.11.3",
+    "dotenv": "^17.3.1",
-    "dotenv": "^16.3.1"
+    "express": "^5.2.1",
+    "pg": "^8.20.0"
   },
   "devDependencies": {
-    "nodemon": "^3.0.1",
+    "jest": "^30.3.0",
-    "jest": "^29.7.0"
+    "nodemon": "^3.1.14",
+    "supertest": "^7.2.2"
   }
 }

backend/scripts/import_cities.js

@@ -0,0 +1,95 @@
+const { Pool } = require('pg');
+const { execSync } = require('child_process');
+const fs = require('fs');
+const readline = require('readline');
+require('dotenv').config();
+
+const DATA_URL = 'https://download.geonames.org/export/dump/cities5000.zip';
+const ZIP_FILE = '/tmp/cities.zip';
+const TXT_FILE = '/tmp/cities5000.txt';
+
+async function importGeoNames() {
+  const pool = new Pool({
+    connectionString: process.env.DATABASE_URL || 'postgresql://line_of_sight:line_of_sight_pass@postgres:5432/line_of_sight'
+  });
+
+  try {
+    console.log('Downloading GeoNames cities5000 (Pop > 5000)...');
+    execSync(`wget -q ${DATA_URL} -O ${ZIP_FILE}`);
+    
+    console.log('Extracting data...');
+    execSync(`unzip -o ${ZIP_FILE} -d /tmp`);
+
+    console.log('Connecting to database...');
+    const client = await pool.connect();
+
+    // Ensure table is clean
+    await client.query('TRUNCATE TABLE cities');
+
+    console.log('Starting stream import...');
+    
+    const fileStream = fs.createReadStream(TXT_FILE);
+    const rl = readline.createInterface({
+      input: fileStream,
+      crlfDelay: Infinity
+    });
+
+    let batch = [];
+    const batchSize = 500;
+    let count = 0;
+
+    for await (const line of rl) {
+      const parts = line.split('\t');
+      if (parts.length < 15) continue;
+
+      const name = parts[1]; // name
+      const lat = parseFloat(parts[4]);
+      const lon = parseFloat(parts[5]);
+      const country = parts[8]; // country code
+      const population = parseInt(parts[14]) || 0;
+
+      batch.push({ name, lat, lon, country, population });
+
+      if (batch.length >= batchSize) {
+        await insertBatch(client, batch);
+        count += batch.length;
+        if (count % 5000 === 0) console.log(`Imported ${count} cities...`);
+        batch = [];
+      }
+    }
+
+    if (batch.length > 0) {
+      await insertBatch(client, batch);
+      count += batch.length;
+    }
+
+    console.log(`SUCCESS: Imported ${count} cities and towns.`);
+    client.release();
+
+  } catch (err) {
+    console.error('ERROR during import:', err);
+  } finally {
+    // Cleanup
+    if (fs.existsSync(ZIP_FILE)) fs.unlinkSync(ZIP_FILE);
+    if (fs.existsSync(TXT_FILE)) fs.unlinkSync(TXT_FILE);
+    await pool.end();
+  }
+}
+
+async function insertBatch(client, batch) {
+  const queryParts = [];
+  const values = [];
+  
+  batch.forEach((city, index) => {
+    const base = index * 5;
+    queryParts.push(`($${base + 1}, $${base + 2}, $${base + 3}, ST_SetSRID(ST_MakePoint($${base + 4}, $${base + 5}), 4326)::geography)`);
+    values.push(city.name, city.population, city.country, city.lon, city.lat);
+  });
+
+  await client.query(
+    `INSERT INTO cities (name, population, country, geom) VALUES ${queryParts.join(',')}`,
+    values
+  );
+}
+
+importGeoNames();

backend/tests/server.test.js

@@ -0,0 +1,74 @@
+const request = require('supertest');
+const { app, calculateDestination } = require('../app/server');
+
+// Mock pg Pool
+jest.mock('pg', () => {
+  const mPool = {
+    query: jest.fn(),
+    on: jest.fn(),
+    end: jest.fn(),
+  };
+  return { Pool: jest.fn(() => mPool) };
+});
+
+const { Pool } = require('pg');
+const pool = new Pool();
+
+describe('Line of Sight Backend', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  describe('calculateDestination', () => {
+    test('should calculate correct destination for North (0 degrees)', () => {
+      const start = { lat: 0, lon: 0 };
+      const dest = calculateDestination(start.lat, start.lon, 0, 111.12); // ~1 degree North
+      expect(dest.lat).toBeCloseTo(1, 1);
+      expect(dest.lon).toBeCloseTo(0, 1);
+    });
+
+    test('should calculate correct destination for East (90 degrees)', () => {
+      const start = { lat: 0, lon: 0 };
+      const dest = calculateDestination(start.lat, start.lon, 90, 111.12); // ~1 degree East at equator
+      expect(dest.lat).toBeCloseTo(0, 1);
+      expect(dest.lon).toBeCloseTo(1, 1);
+    });
+  });
+
+  describe('GET /api/health', () => {
+    test('should return 200 OK', async () => {
+      const response = await request(app).get('/api/health');
+      expect(response.status).toBe(200);
+      expect(response.body.status).toBe('ok');
+    });
+  });
+
+  describe('GET /api/line-of-sight', () => {
+    test('should return valid response structure', async () => {
+      // Mock the water checks and the main city query
+      pool.query
+        .mockResolvedValueOnce({ rows: [{ has_land: true }] }) // Simplified for tests, it actually calls many times
+        .mockResolvedValue({ rows: [{ id: 1, name: 'London', population: 9000000, country: 'GB', lat: 51.5, lon: -0.1, distance_off_line_km: 0, distance_from_start_km: 0, pos_on_line: 0 }] });
+
+      const response = await request(app)
+        .get('/api/line-of-sight')
+        .query({ lat: 51.5, lon: -0.1, direction: 45, tolerance: 50 });
+
+      expect(response.status).toBe(200);
+      expect(response.body.success).toBe(true);
+      expect(response.body.data.conurbations).toBeDefined();
+      expect(response.body.data.line_coordinates).toBeDefined();
+    });
+
+    test('should handle database errors', async () => {
+      pool.query.mockRejectedValue(new Error('DB Error'));
+
+      const response = await request(app)
+        .get('/api/line-of-sight')
+        .query({ lat: 51.5, lon: -0.1, direction: 45, tolerance: 50 });
+
+      expect(response.status).toBe(500);
+      expect(response.body.success).toBe(false);
+    });
+  });
+});

docker-compose.yml

@@ -2,16 +2,18 @@ version: '3.8'
 
 services:
   postgres:
-    image: postgis/postgis:15-3.3-alpine
+    image: kartoza/postgis:latest
+    platform: linux/arm64
     container_name: line-of-sight-db
     environment:
-      POSTGRES_DB: line_of_sight
+      - POSTGRES_DB=line_of_sight
-      POSTGRES_USER: line_of_sight
+      - POSTGRES_USER=line_of_sight
-      POSTGRES_PASSWORD: line_of_sight_pass
+      - POSTGRES_PASS=line_of_sight_pass
+      - ALLOW_IP_RANGE=0.0.0.0/0
     ports:
       - "5432:5432"
     volumes:
-      - pgdata:/var/lib/postgresql/data
+      - pgdata:/var/lib/postgresql
       - ./docker/init.sql:/docker-entrypoint-initdb.d/init.sql
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -U line_of_sight"]
@@ -42,9 +44,9 @@ services:
       dockerfile: Dockerfile
     container_name: line-of-sight-frontend
     ports:
-      - "3000:3000"
+      - "3050:3050"
     environment:
-      - REACT_APP_API_URL=http://localhost:3001/api
+      - VITE_API_URL=http://localhost:3001/api
     depends_on:
       - backend
     volumes:

frontend/Dockerfile

@@ -1,4 +1,4 @@
-FROM node:18-alpine
+FROM node:24-alpine
 
 WORKDIR /app
 
@@ -10,10 +10,10 @@ RUN npm install
 COPY . .
 
 # Expose port
-EXPOSE 3000
+EXPOSE 3050
 
 # Set environment variable for API URL
-ENV REACT_APP_API_URL=http://localhost:3001/api
+ENV VITE_API_URL=http://localhost:3001/api
 
 # Start development server
 CMD ["npm", "start"]

frontend/e2e/app.spec.js

@@ -0,0 +1,104 @@
+import { test, expect } from '@playwright/test';
+
+// MapLibre GL requires WebGL which isn't available in headless Chromium.
+// Intercept the module request and return a lightweight mock so React can render.
+const MAPLIBRE_MOCK = `
+class Map {
+  constructor(opts) {
+    this._listeners = {};
+    Promise.resolve().then(() => this._emit('style.load'));
+  }
+  _emit(event) {
+    (this._listeners[event] || []).forEach(fn => fn());
+  }
+  on(event, fn) {
+    if (!this._listeners[event]) this._listeners[event] = [];
+    this._listeners[event].push(fn);
+    return this;
+  }
+  off(event, fn) {
+    this._listeners[event] = (this._listeners[event] || []).filter(l => l !== fn);
+    return this;
+  }
+  remove() {}
+  getSource() { return null; }
+  getLayer() { return null; }
+  addSource() {}
+  addLayer() {}
+  removeLayer() {}
+  removeSource() {}
+  setSky() {}
+  setTerrain() {}
+  setLayoutProperty() {}
+  flyTo() {}
+  jumpTo() {}
+  setStyle() { Promise.resolve().then(() => this._emit('style.load')); }
+  getCanvas() { return document.createElement('canvas'); }
+  project() { return { x: 0, y: 0 }; }
+  unproject() { return { lng: 0, lat: 0 }; }
+}
+class Marker {
+  constructor(opts) {
+    this._el = (opts && opts.element) || document.createElement('div');
+  }
+  setLngLat() { return this; }
+  addTo() { return this; }
+  remove() {}
+  getLngLat() { return { lng: 0, lat: 0 }; }
+  getElement() { return this._el; }
+}
+class Popup {
+  setLngLat() { return this; }
+  setDOMContent() { return this; }
+  addTo() { return this; }
+  remove() {}
+}
+class LngLatBounds {
+  extend() { return this; }
+}
+export default { Map, Marker, Popup, LngLatBounds };
+`;
+
+test.beforeEach(async ({ page }) => {
+  await page.route('**maplibre-gl.js*', async route => {
+    await route.fulfill({ contentType: 'application/javascript', body: MAPLIBRE_MOCK });
+  });
+});
+
+test.describe('Line of Sight Application', () => {
+  test('should load the home page and show settings', async ({ page }) => {
+    await page.goto('/');
+    await expect(page.locator('text=Line of Sight Settings')).toBeVisible();
+    await expect(page.locator('label:has-text("Direction")')).toBeVisible();
+  });
+
+  test('should be able to toggle map style', async ({ page }) => {
+    await page.goto('/');
+    await page.waitForSelector('h3:text("Line of Sight Settings")', { timeout: 10000 });
+    const darkButton = page.locator('button:text("Dark")');
+    await darkButton.click();
+    await expect(darkButton).toHaveClass(/active-style/);
+  });
+
+  test('should show results when clicking the search button', async ({ page }) => {
+    await page.goto('/');
+    await page.waitForSelector('h3:text("Line of Sight Settings")', { timeout: 10000 });
+
+    await page.route('**/api/line-of-sight*', async route => {
+      const json = {
+        success: true,
+        data: {
+          conurbations: [
+            { id: 1, name: 'Test City', population: 100000, country: 'TS', lat: 0, lon: 0, distance_km: 10, off_line_km: 1 }
+          ],
+          line_coordinates: [{ lat: 0, lon: 0 }, { lat: 1, lon: 1 }]
+        }
+      };
+      await route.fulfill({ json });
+    });
+
+    await page.click('button:text("Show Line of Sight")');
+    await expect(page.locator('text=Conurbations Found')).toBeVisible();
+    await expect(page.locator('text=Test City')).toBeVisible();
+  });
+});

frontend/index.html

@@ -11,5 +11,6 @@
 </head>
 <body>
     <div id="root"></div>
+    <script type="module" src="/src/index.jsx"></script>
 </body>
 </html>

frontend/package.json

@@ -3,20 +3,38 @@
   "version": "1.0.0",
   "private": true,
   "dependencies": {
-    "react": "^18.2.0",
+    "@turf/turf": "^7.3.4",
-    "react-dom": "^18.2.0",
+    "axios": "^1.7.9",
-    "react-scripts": "5.0.1",
+    "maplibre-gl": "^5.20.1",
-    "maplibre-gl": "^3.6.2",
+    "react": "^19.2.1",
-    "axios": "^1.6.2"
+    "react-dom": "^19.2.1"
+  },
+  "devDependencies": {
+    "@playwright/test": "^1.58.2",
+    "@testing-library/jest-dom": "^6.6.0",
+    "@testing-library/react": "^16.1.0",
+    "@vitejs/plugin-react": "^4.3.0",
+    "happy-dom": "^20.8.4",
+    "vite": "^6.0.0",
+    "vitest": "^3.0.0"
   },
   "scripts": {
-    "start": "react-scripts start",
+    "start": "vite",
-    "build": "react-scripts build",
+    "build": "vite build",
-    "test": "react-scripts test",
+    "preview": "vite preview",
-    "eject": "react-scripts eject"
+    "test": "vitest",
+    "test:e2e": "playwright test"
   },
   "browserslist": {
-    "production": [">0.2%", "not dead", "not op_mini all"],
+    "production": [
-    "development": ["last 1 chrome version", "last 1 firefox version", "last 1 safari version"]
+      ">0.2%",
+      "not dead",
+      "not op_mini all"
+    ],
+    "development": [
+      "last 1 chrome version",
+      "last 1 firefox version",
+      "last 1 safari version"
+    ]
   }
 }

frontend/playwright.config.js

@@ -0,0 +1,34 @@
+import { defineConfig, devices } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './e2e',
+  fullyParallel: true,
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 2 : 0,
+  workers: process.env.CI ? 1 : undefined,
+  reporter: process.env.CI ? 'list' : 'html',
+  use: {
+    baseURL: 'http://localhost:3050',
+    trace: 'on-first-retry',
+    headless: true,
+    launchOptions: {
+      args: [
+        '--enable-webgl',
+        '--ignore-gpu-blocklist',
+        '--use-gl=angle',
+        '--use-angle=swiftshader-webgl',
+      ],
+    },
+  },
+  projects: [
+    {
+      name: 'chromium',
+      use: { ...devices['Desktop Chrome'] },
+    },
+  ],
+  webServer: {
+    command: 'npm run start',
+    url: 'http://localhost:3050',
+    reuseExistingServer: !process.env.CI,
+  },
+});

frontend/src/App.js

@@ -1,243 +0,0 @@
-import React, { useState, useEffect, useRef } from 'react';
-import maplibregl from 'maplibre-gl';
-import 'maplibre-gl/dist/maplibre-gl.css';
-import apiService from './services/api';
-import './styles/App.css';
-
-const APP = () => {
-  const mapContainerRef = useRef(null);
-  const mapRef = useRef(null);
-  const [selectedPoint, setSelectedPoint] = useState({ lat: 51.5074, lon: -0.1278 });
-  const [direction, setDirection] = useState(45);
-  const [lineOfSightData, setLineOfSightData] = useState(null);
-  const [loading, setLoading] = useState(false);
-  const [mapStyle, setMapStyle] = useState('light'); // 'light' or 'dark'
-  const [tolerance, setTolerance] = useState(50);
-
-  useEffect(() => {
-    // Initialize MapLibre map
-    mapRef.current = new maplibregl.Map({
-      container: mapContainerRef.current,
-      style: getMapStyle(mapStyle),
-      center: [-0.1278, 51.5074], // London
-      zoom: 3,
-      pitch: 0
-    });
-
-    mapRef.current.on('load', () => {
-      console.log('Map loaded successfully');
-    });
-
-    mapRef.current.on('click', (e) => {
-      const { lng, lat } = e.lngLat;
-      setSelectedPoint({ lat, lon: lng });
-      
-      // Clear previous line
-      if (mapRef.current.getSource('line-of-sight')) {
-        mapRef.current.removeLayer('line-of-sight');
-        mapRef.current.removeSource('line-of-sight');
-      }
-    });
-
-    return () => {
-      mapRef.current.remove();
-    };
-  }, []);
-
-  useEffect(() => {
-    // Update map style when toggle changes
-    if (mapRef.current) {
-      mapRef.current.setStyle(getMapStyle(mapStyle));
-    }
-  }, [mapStyle]);
-
-  const getMapStyle = (style) => {
-    return style === 'dark' 
-      ? 'https://demotiles.maplibre.org/style.json' 
-      : 'https://demotiles.maplibre.org/style.json'; // Using same for now, can be customized
-  };
-
-  const handleShowLineOfSight = async () => {
-    setLoading(true);
-    try {
-      const response = await apiService.getLineOfSight(
-        selectedPoint.lat, 
-        selectedPoint.lon, 
-        direction, 
-        tolerance
-      );
-      
-      setLineOfSightData(response.data);
-      renderLineOnMap(response.data);
-    } catch (error) {
-      console.error('Error fetching line of sight:', error);
-    } finally {
-      setLoading(false);
-    }
-  };
-
-  const renderLineOnMap = (data) => {
-    const map = mapRef.current;
-    if (!map) return;
-
-    // Clear existing line
-    if (map.getSource('line-of-sight')) {
-      map.removeLayer('line-of-sight');
-      map.removeSource('line-of-sight');
-    }
-
-    // Add line source
-    map.addSource('line-of-sight', {
-      type: 'geojson',
-      data: {
-        type: 'Feature',
-        properties: {},
-        geometry: {
-          type: 'LineString',
-          coordinates: data.line_coordinates.map(coord => [coord.lon, coord.lat])
-        }
-      }
-    });
-
-    // Add line layer
-    map.addLayer({
-      id: 'line-of-sight',
-      type: 'line',
-      source: 'line-of-sight',
-      layout: {
-        'line-join': 'round',
-        'line-cap': 'round'
-      },
-      paint: {
-        'line-color': '#FF6B6B',
-        'line-width': 4,
-        'line-opacity': 0.8
-      }
-    });
-
-    // Add city markers
-    data.conurbations.forEach((city, index) => {
-      const markerId = `city-${index}`;
-      
-      // Create marker element
-      const el = document.createElement('div');
-      el.className = 'city-marker';
-      el.innerHTML = `
-        <div class="marker-dot"></div>
-        <div class="marker-label">${city.name}</div>
-        <div class="marker-pop">${(city.population / 1000000).toFixed(1)}M</div>
-      `;
-
-      // Add marker to map
-      new maplibregl.Marker(el)
-        .setLngLat([city.lon, city.lat])
-        .setPopup(new maplibregl.Popup().setHTML(
-          `<strong>${city.name}</strong><br/>Population: ${city.population.toLocaleString()}<br/>Distance: ${city.distance_km} km`
-        ))
-        .addTo(map);
-    });
-
-    // Fit bounds to show line
-    const bounds = new maplibregl.LngLatBounds();
-    data.line_coordinates.forEach(coord => {
-      bounds.extend([coord.lon, coord.lat]);
-    });
-    map.fitBounds(bounds, { padding: 50 });
-  };
-
-  return (
-    <div className="app-container">
-      <div className="map-container" ref={mapContainerRef}></div>
-      
-      <div className="controls">
-        <div className="control-group">
-          <h3>Line of Sight Settings</h3>
-          
-          <div className="setting-row">
-            <label>Start Point:</label>
-            <span>{selectedPoint.lat.toFixed(4)}, {selectedPoint.lon.toFixed(4)}</span>
-          </div>
-
-          <div className="setting-row">
-            <label>Direction (0-360°):</label>
-            <input 
-              type="range" 
-              min="0" 
-              max="360" 
-              value={direction} 
-              onChange={(e) => setDirection(parseInt(e.target.value))}
-            />
-            <span>{direction}°</span>
-          </div>
-
-          <div className="setting-row">
-            <label>Fuzziness Tolerance (km):</label>
-            <input 
-              type="number" 
-              value={tolerance} 
-              onChange={(e) => setTolerance(parseInt(e.target.value))}
-              min="10"
-              max="200"
-            />
-            <span>{tolerance} km</span>
-          </div>
-
-          <div className="setting-row">
-            <label>Map Style:</label>
-            <button onClick={() => setMapStyle('light')}>Light</button>
-            <button onClick={() => setMapStyle('dark')}>Dark</button>
-          </div>
-
-          <button 
-            className="action-btn" 
-            onClick={handleShowLineOfSight} 
-            disabled={loading}
-          >
-            {loading ? 'Calculating...' : '📡 Show Line of Sight'}
-          </button>
-        </div>
-
-        {lineOfSightData && (
-          <div className="results-panel">
-            <h3>Conurbations Found ({lineOfSightData.conurbations.length})</h3>
-            <table>
-              <thead>
-                <tr>
-                  <th>#</th>
-                  <th>City</th>
-                  <th>Population</th>
-                  <th>Distance</th>
-                </tr>
-              </thead>
-              <tbody>
-                {lineOfSightData.conurbations.slice(0, 10).map((city, index) => (
-                  <tr key={city.id}>
-                    <td>{index + 1}</td>
-                    <td>{city.name}</td>
-                    <td>{(city.population / 1000000).toFixed(1)}M</td>
-                    <td>{city.distance_km} km</td>
-                  </tr>
-                ))}
-              </tbody>
-            </table>
-            {lineOfSightData.conurbations.length > 10 && (
-              <p className="more-info">... and {lineOfSightData.conurbations.length - 10} more cities</p>
-            )}
-          </div>
-        )}
-
-        <div className="instructions">
-          <h3>How to Use</h3>
-          <ol>
-            <li>Click anywhere on the map to select a starting point</li>
-            <li>Adjust the direction using the slider (0-360°)</li>
-            <li>Set your fuzziness tolerance (how close cities must be to the line)</li>
-            <li>Click "Show Line of Sight" to visualize the path and cities</li>
-          </ol>
-        </div>
-      </div>
-    </div>
-  );
-};
-
-export default APP;

frontend/src/App.jsx

@@ -0,0 +1,686 @@
+import React, { useState, useEffect, useRef } from 'react';
+import maplibregl from 'maplibre-gl';
+import 'maplibre-gl/dist/maplibre-gl.css';
+import * as turf from '@turf/turf';
+import apiService from './services/api';
+import './styles/App.css';
+
+const APP = () => {
+  const mapContainerRef = useRef(null);
+  const mapRef = useRef(null);
+  const startMarkerRef = useRef(null);
+  const cityMarkersRef = useRef([]);
+  const animationRef = useRef(null);
+  const popupRef = useRef(null);
+  const [selectedPoint, setSelectedPoint] = useState({ lat: 51.5074, lon: -0.1278 });
+  const [direction, setDirection] = useState(45);
+  const [lineOfSightData, setLineOfSightData] = useState(null);
+  const [loading, setLoading] = useState(false);
+  const [isPlaying, setIsPlaying] = useState(false);
+  const [flightSpeed, setFlightSpeed] = useState(1.0);
+  const [mapStyle, setMapStyle] = useState('light'); // 'light' or 'dark'
+  const [tolerance, setTolerance] = useState(50);
+  const [selectedCity, setSelectedCity] = useState(null);
+  const [isLocked, setIsLocked] = useState(false);
+
+  useEffect(() => {
+    // Initialize MapLibre map - ONLY ONCE
+    mapRef.current = new maplibregl.Map({
+      container: mapContainerRef.current,
+      style: getMapStyle(mapStyle),
+      center: [-0.1278, 51.5074], // London
+      zoom: 2,
+      pitch: 0,
+      projection: 'globe' // Enable 3D Globe
+    });
+
+    mapRef.current.on('style.load', () => {
+      console.log('Map style loaded or changed');
+      setupMapLayers();
+    });
+
+    return () => {
+      if (animationRef.current) cancelAnimationFrame(animationRef.current);
+      if (mapRef.current) mapRef.current.remove();
+    };
+  }, []); // Run only once
+
+  const setupMapLayers = () => {
+    const map = mapRef.current;
+    if (!map) return;
+
+    // 1. Add atmosphere/sky effects
+    map.setSky({
+      'sky-color': '#199EF3',
+      'sky-horizon-blend': 0.5,
+      'horizon-color': '#ffffff',
+      'horizon-fog-blend': 0.5,
+      'fog-color': '#add8e6',
+      'fog-ground-blend': 0.5
+    });
+    
+    // 2. Add terrain source for 3D effect
+    if (!map.getSource('terrain')) {
+      map.addSource('terrain', {
+        type: 'raster-dem',
+        tiles: ['https://s3.amazonaws.com/elevation-tiles-prod/terrarium/{z}/{x}/{y}.png'],
+        encoding: 'terrarium',
+        tileSize: 256,
+        maxzoom: 15
+      });
+    }
+    map.setTerrain({ source: 'terrain', exaggeration: 1.5 });
+
+    // 3. Initialize start marker
+    if (startMarkerRef.current) startMarkerRef.current.remove();
+    startMarkerRef.current = new maplibregl.Marker({ color: '#FF6B6B' })
+      .setLngLat([selectedPoint.lon, selectedPoint.lat])
+      .addTo(map);
+
+    // 4. Initialize preview line source and layer
+    if (!map.getSource('preview-line')) {
+      map.addSource('preview-line', {
+        type: 'geojson',
+        data: {
+          type: 'Feature',
+          geometry: {
+            type: 'LineString',
+            coordinates: []
+          }
+        }
+      });
+
+      map.addLayer({
+        id: 'preview-line',
+        type: 'line',
+        source: 'preview-line',
+        paint: {
+          'line-color': '#FF6B6B',
+          'line-width': 2,
+          'line-dasharray': [2, 2]
+        }
+      });
+    }
+
+    // 5. Restore results line and city markers if they existed
+    if (lineOfSightData) {
+      renderLineOnMap(lineOfSightData);
+      // Hide preview if results are shown
+      if (map.getLayer('preview-line')) {
+        map.setLayoutProperty('preview-line', 'visibility', 'none');
+      }
+    } else {
+      updatePreviewLine(selectedPoint, direction);
+    }
+  };
+
+  // Separate effect for the click listener that respects isLocked
+  useEffect(() => {
+    if (!mapRef.current) return;
+
+    const handleClick = (e) => {
+      // Don't allow moving start point if locked
+      if (isLocked) return;
+
+      const { lng, lat } = e.lngLat;
+      setSelectedPoint({ lat, lon: lng });
+      
+      if (startMarkerRef.current) {
+        startMarkerRef.current.setLngLat([lng, lat]);
+      }
+
+      // Clear previous final results when moving start point
+      clearCityMarkers();
+      if (mapRef.current.getSource('line-of-sight')) {
+        mapRef.current.removeLayer('line-of-sight');
+        mapRef.current.removeSource('line-of-sight');
+      }
+    };
+
+    mapRef.current.on('click', handleClick);
+    return () => {
+      if (mapRef.current) mapRef.current.off('click', handleClick);
+    };
+  }, [isLocked]); 
+
+  const handleStartAgain = () => {
+    if (animationRef.current) {
+      cancelAnimationFrame(animationRef.current);
+      setIsPlaying(false);
+      setFlightSpeed(1.0);
+    }
+    
+    if (popupRef.current) {
+      popupRef.current.remove();
+      popupRef.current = null;
+    }
+
+    setIsLocked(false);
+    setLineOfSightData(null);
+    setSelectedCity(null);
+    clearCityMarkers();
+    
+    if (mapRef.current) {
+      if (mapRef.current.getSource('line-of-sight')) {
+        mapRef.current.removeLayer('line-of-sight');
+        mapRef.current.removeSource('line-of-sight');
+      }
+      // Re-enable preview line if it was hidden
+      if (mapRef.current.getLayer('preview-line')) {
+        mapRef.current.setLayoutProperty('preview-line', 'visibility', 'visible');
+      }
+      
+      // Reset map pitch and zoom
+      mapRef.current.flyTo({
+        center: [selectedPoint.lon, selectedPoint.lat],
+        zoom: 3,
+        pitch: 0,
+        bearing: 0
+      });
+    }
+  };
+
+  const clearCityMarkers = () => {
+    if (cityMarkersRef.current) {
+      cityMarkersRef.current.forEach(marker => marker.remove());
+      cityMarkersRef.current = [];
+    }
+  };
+
+  const getCountryName = (code) => {
+    try {
+      const regionNames = new Intl.DisplayNames(['en'], { type: 'region' });
+      return regionNames.of(code.toUpperCase()) || code;
+    } catch (e) {
+      return code;
+    }
+  };
+
+  const showCityPopup = (city) => {
+    if (!mapRef.current) return;
+
+    if (popupRef.current) popupRef.current.remove();
+
+    const popupNode = document.createElement('div');
+    popupNode.className = 'map-info-popup';
+    const countryName = getCountryName(city.country);
+    
+    popupNode.innerHTML = `
+      <div class="popup-header">
+        <strong>${city.name}</strong>, ${countryName}
+      </div>
+      <div class="popup-body">
+        <p>Population: ${city.population.toLocaleString()}</p>
+        <p>Dist. from start: ${city.distance_km} km</p>
+        <p>Deviation: ${city.off_line_km} km</p>
+      </div>
+    `;
+
+    popupRef.current = new maplibregl.Popup({ 
+      closeButton: true, 
+      closeOnClick: false,
+      maxWidth: '300px',
+      offset: [0, -20]
+    })
+      .setLngLat([city.lon, city.lat])
+      .setDOMContent(popupNode)
+      .addTo(mapRef.current);
+    
+    popupRef.current.on('close', () => {
+      setSelectedCity(null);
+    });
+  };
+
+  const startFlyOver = () => {
+    if (!lineOfSightData || !mapRef.current) return;
+    
+    if (isPlaying) {
+      if (animationRef.current) cancelAnimationFrame(animationRef.current);
+      setIsPlaying(false);
+      setFlightSpeed(1.0);
+      return;
+    }
+
+    setIsPlaying(true);
+    setSelectedCity(null);
+    if (popupRef.current) popupRef.current.remove();
+    
+    const coordinates = lineOfSightData.line_coordinates.map(c => [c.lon, c.lat]);
+    const route = turf.lineString(coordinates);
+    const routeDistance = turf.length(route);
+    const startTime = performance.now();
+
+    let lastNearestCityId = null;
+    let lastFetchedDist = 0;
+    let currentProgress = 0;
+    let lastTimestamp = performance.now();
+    let currentSpeedMultiplier = 1.0;
+    let frameCount = 0;
+
+    async function animate(currentTime) {
+      if (!mapRef.current) return;
+      
+      const deltaTime = currentTime - lastTimestamp;
+      lastTimestamp = currentTime;
+
+      const baseKmPerMs = 0.1; // 100km per second
+      
+      const pathPoints = lineOfSightData.line_coordinates;
+      const pointIndex = Math.min(
+        Math.floor((currentProgress / routeDistance) * pathPoints.length),
+        pathPoints.length - 1
+      );
+      const isOverWater = pathPoints[pointIndex]?.is_over_water;
+
+      // Predictive land detection (look ahead 2000km)
+      let futureIsOverWater = true;
+      const lookAheadDistance = 2000;
+      const lookAheadSteps = 10;
+      for (let i = 1; i <= lookAheadSteps; i++) {
+        const checkDist = currentProgress + (lookAheadDistance * i) / lookAheadSteps;
+        const checkIndex = Math.min(
+          Math.floor((checkDist / routeDistance) * pathPoints.length),
+          pathPoints.length - 1
+        );
+        if (pathPoints[checkIndex] && !pathPoints[checkIndex].is_over_water) {
+          futureIsOverWater = false;
+          break;
+        }
+      }
+
+      const targetMultiplier = (isOverWater && futureIsOverWater) ? 20.0 : 1.0;
+      const acceleration = 0.005;
+      
+      if (currentSpeedMultiplier < targetMultiplier) {
+        currentSpeedMultiplier = Math.min(currentSpeedMultiplier + acceleration * deltaTime, targetMultiplier);
+      } else if (currentSpeedMultiplier > targetMultiplier) {
+        currentSpeedMultiplier = Math.max(currentSpeedMultiplier - acceleration * deltaTime, targetMultiplier);
+      }
+
+      frameCount++;
+      if (frameCount % 10 === 0) {
+        setFlightSpeed(currentSpeedMultiplier);
+      }
+
+      currentProgress += baseKmPerMs * deltaTime * currentSpeedMultiplier;
+      
+      const phase = Math.min(currentProgress / routeDistance, 1);
+      
+      if (phase >= 1) {
+        setIsPlaying(false);
+        setFlightSpeed(1.0);
+        return;
+      }
+      
+      const eye = turf.along(route, currentProgress).geometry.coordinates;
+      const target = turf.along(route, Math.min(currentProgress + 10, routeDistance)).geometry.coordinates;
+      
+      const bearing = turf.bearing(turf.point(eye), turf.point(target));
+
+      mapRef.current.jumpTo({
+        center: eye,
+        zoom: 6,
+        pitch: 65,
+        bearing: bearing
+      });
+
+      if (currentProgress - lastFetchedDist > 2000) {
+        lastFetchedDist = currentProgress;
+        try {
+          const response = await apiService.getLineOfSight(
+            eye[1], eye[0], bearing, tolerance
+          );
+          
+          if (response.data.success) {
+            const newCities = response.data.data.conurbations;
+            setLineOfSightData(prev => {
+              const existingIds = new Set(prev.conurbations.map(c => c.id));
+              const uniqueNewCities = newCities.filter(c => !existingIds.has(c.id));
+              const adjustedCities = uniqueNewCities.map(c => ({
+                ...c,
+                distance_km: Math.round(c.distance_km + currentProgress)
+              }));
+              const updatedData = {
+                ...prev,
+                conurbations: [...prev.conurbations, ...adjustedCities].sort((a, b) => a.distance_km - b.distance_km)
+              };
+              addMarkersToMap(adjustedCities, prev.conurbations.length);
+              return updatedData;
+            });
+          }
+        } catch (e) {
+          console.error('Error fetching more cities during flight:', e);
+        }
+      }
+
+      const nearestCity = lineOfSightData.conurbations.find(city => 
+        Math.abs(city.distance_km - currentProgress) < 100 
+      );
+
+      if (nearestCity && nearestCity.id !== lastNearestCityId) {
+        lastNearestCityId = nearestCity.id;
+        setSelectedCity(nearestCity);
+        showCityPopup(nearestCity);
+      }
+      
+      animationRef.current = requestAnimationFrame(animate);
+    }
+    
+    animationRef.current = requestAnimationFrame(animate);
+  };
+
+  const addMarkersToMap = (cities, startIndex = 0) => {
+    const map = mapRef.current;
+    if (!map) return;
+
+    cities.forEach((city, index) => {
+      const displayIndex = startIndex + index + 1;
+      
+      const el = document.createElement('div');
+      el.className = 'city-marker';
+      el.innerHTML = `
+        <div class="marker-number">${displayIndex}</div>
+        <div class="marker-dot"></div>
+        <div class="marker-label">${city.name}</div>
+        <div class="marker-pop">${(city.population / 1000).toFixed(0)}k</div>
+      `;
+
+      const marker = new maplibregl.Marker(el)
+        .setLngLat([city.lon, city.lat])
+        .addTo(map);
+      
+      marker.getElement().addEventListener('click', (e) => {
+        e.stopPropagation();
+        setSelectedCity(city);
+        showCityPopup(city);
+      });
+      
+      cityMarkersRef.current.push(marker);
+    });
+  };
+
+  const renderLineOnMap = (data) => {
+    const map = mapRef.current;
+    if (!map) return;
+
+    clearCityMarkers();
+    if (map.getSource('line-of-sight')) {
+      map.removeLayer('line-of-sight');
+      map.removeSource('line-of-sight');
+    }
+
+    map.addSource('line-of-sight', {
+      type: 'geojson',
+      data: {
+        type: 'Feature',
+        properties: {},
+        geometry: {
+          type: 'LineString',
+          coordinates: data.line_coordinates.map(coord => [coord.lon, coord.lat])
+        }
+      }
+    });
+
+    map.addLayer({
+      id: 'line-of-sight',
+      type: 'line',
+      source: 'line-of-sight',
+      layout: {
+        'line-join': 'round',
+        'line-cap': 'round'
+      },
+      paint: {
+        'line-color': '#FF6B6B',
+        'line-width': 4,
+        'line-opacity': 0.8
+      }
+    });
+
+    addMarkersToMap(data.conurbations);
+
+    const bounds = new maplibregl.LngLatBounds();
+    data.line_coordinates.forEach(coord => {
+      bounds.extend([coord.lon, coord.lat]);
+    });
+    map.fitBounds(bounds, { padding: 50 });
+  };
+
+  const updatePreviewLine = (point, bearing) => {
+    const map = mapRef.current;
+    if (!map || !map.getSource('preview-line')) return;
+
+    const path = [];
+    const steps = 50;
+    const totalDistance = 20000;
+
+    for (let i = 0; i <= steps; i++) {
+      const dist = (totalDistance * i) / steps;
+      path.push(calculateDestination(point.lat, point.lon, bearing, dist));
+    }
+    
+    map.getSource('preview-line').setData({
+      type: 'Feature',
+      geometry: {
+        type: 'LineString',
+        coordinates: path.map(p => [p.lon, p.lat])
+      }
+    });
+  };
+
+  const calculateDestination = (lat, lon, bearing, distance) => {
+    const R = 6371; 
+    const brng = (bearing * Math.PI) / 180;
+    const φ1 = (lat * Math.PI) / 180;
+    const λ1 = (lon * Math.PI) / 180;
+    const δ = distance / R;
+
+    const φ2 = Math.asin(
+      Math.sin(φ1) * Math.cos(δ) +
+        Math.cos(φ1) * Math.sin(δ) * Math.cos(brng)
+    );
+    const λ2 =
+      λ1 +
+      Math.atan2(
+        Math.sin(brng) * Math.sin(δ) * Math.cos(φ1),
+        Math.cos(δ) - Math.sin(φ1) * Math.sin(φ2)
+      );
+
+    return {
+      lat: (φ2 * 180) / Math.PI,
+      lon: (((λ2 * 180) / Math.PI + 540) % 360) - 180
+    };
+  };
+
+  useEffect(() => {
+    if (mapRef.current) {
+      mapRef.current.setStyle(getMapStyle(mapStyle));
+    }
+  }, [mapStyle]);
+
+  const getMapStyle = (style) => {
+    if (style === 'satellite') {
+      return {
+        version: 8,
+        sources: {
+          'esri-satellite': {
+            type: 'raster',
+            tiles: ['https://services.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}'],
+            tileSize: 256,
+            attribution: 'Tiles &copy; Esri &mdash; Source: Esri, i-cubed, USDA, USGS, AEX, GeoEye, Getmapping, Aerogrid, IGN, IGP, UPR-EGP, and the GIS User Community'
+          }
+        },
+        layers: [
+          {
+            id: 'satellite-layer',
+            type: 'raster',
+            source: 'esri-satellite',
+            minzoom: 0,
+            maxzoom: 20
+          }
+        ]
+      };
+    }
+    return style === 'dark' 
+      ? 'https://demotiles.maplibre.org/style.json' 
+      : 'https://demotiles.maplibre.org/style.json';
+  };
+
+  const handleShowLineOfSight = async () => {
+    setLoading(true);
+    setSelectedCity(null);
+    try {
+      const response = await apiService.getLineOfSight(
+        selectedPoint.lat, 
+        selectedPoint.lon, 
+        direction, 
+        tolerance
+      );
+      
+      setLineOfSightData(response.data.data);
+      setIsLocked(true); 
+      
+      if (mapRef.current && mapRef.current.getLayer('preview-line')) {
+        mapRef.current.setLayoutProperty('preview-line', 'visibility', 'none');
+      }
+      
+      renderLineOnMap(response.data.data);
+    } catch (error) {
+      console.error('Error fetching line of sight:', error);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <div className="app-container">
+      <div className="map-container" ref={mapContainerRef}>
+      </div>
+      
+      <div className="controls">
+        <div className={`control-group ${isLocked ? 'disabled-controls' : ''}`}>
+          <h3>Line of Sight Settings</h3>
+          
+          <div className="setting-row">
+            <label>Start Point:</label>
+            <span>{selectedPoint.lat.toFixed(4)}, {selectedPoint.lon.toFixed(4)}</span>
+          </div>
+
+          <div className="setting-row">
+            <label>Direction (0-360°):</label>
+            <input 
+              type="range" 
+              min="0" 
+              max="360" 
+              value={direction} 
+              disabled={isLocked}
+              onChange={(e) => setDirection(parseInt(e.target.value))}
+            />
+            <span>{direction}°</span>
+          </div>
+
+          <div className="setting-row">
+            <label>Fuzziness Tolerance (km):</label>
+            <input 
+              type="number" 
+              value={tolerance} 
+              disabled={isLocked}
+              onChange={(e) => setTolerance(parseInt(e.target.value))}
+              min="10"
+              max="200"
+            />
+            <span>{tolerance} km</span>
+          </div>
+
+          <div className="setting-row">
+            <label>Map Style:</label>
+            <button 
+              className={mapStyle === 'light' ? 'active-style' : ''} 
+              onClick={() => setMapStyle('light')}
+            >Light</button>
+            <button 
+              className={mapStyle === 'dark' ? 'active-style' : ''} 
+              onClick={() => setMapStyle('dark')}
+            >Dark</button>
+            <button 
+              className={mapStyle === 'satellite' ? 'active-style' : ''} 
+              onClick={() => setMapStyle('satellite')}
+            >Satellite</button>
+          </div>
+
+          {!isLocked ? (
+            <button 
+              className="action-btn" 
+              onClick={handleShowLineOfSight} 
+              disabled={loading}
+            >
+              {loading ? 'Calculating...' : '📡 Show Line of Sight'}
+            </button>
+          ) : (
+            <>
+              <button 
+                className="action-btn" 
+                onClick={startFlyOver}
+                style={{ backgroundColor: isPlaying ? '#e74c3c' : '#3498db' }}
+              >
+                {isPlaying ? `⏹ Stop Flight (${flightSpeed.toFixed(1)}x)` : '✈️ Fly Over Route'}
+              </button>
+              <button 
+                className="action-btn-secondary" 
+                onClick={handleStartAgain}
+              >
+                🔄 Start Again
+              </button>
+            </>
+          )}
+        </div>
+
+        {lineOfSightData && (
+          <div className="results-panel">
+            <h3>Conurbations Found ({lineOfSightData.conurbations.length})</h3>
+            <p className="hint">Click a city for details</p>
+            <table>
+              <thead>
+                <tr>
+                  <th>#</th>
+                  <th>City</th>
+                  <th>Population</th>
+                  <th>Dist.</th>
+                </tr>
+              </thead>
+              <tbody>
+                {lineOfSightData.conurbations.map((city, index) => (
+                  <tr 
+                    key={city.id} 
+                    onClick={() => {
+                      setSelectedCity(city);
+                      showCityPopup(city);
+                      mapRef.current.flyTo({ center: [city.lon, city.lat], zoom: 8 });
+                    }}
+                    className={selectedCity?.id === city.id ? 'selected-row' : ''}
+                  >
+                    <td>{index + 1}</td>
+                    <td>{city.name}</td>
+                    <td>{(city.population / 1000).toFixed(0)}k</td>
+                    <td>{city.distance_km}km</td>
+                  </tr>
+                ))}
+              </tbody>
+            </table>
+          </div>
+        )}
+
+        <div className="instructions">
+          <h3>How to Use</h3>
+          <ol>
+            <li>Click anywhere on the map to select a starting point</li>
+            <li>Adjust the direction using the slider (0-360°)</li>
+            <li>Set your fuzziness tolerance (how close cities must be to the line)</li>
+            <li>Click "Show Line of Sight" to visualize the path and cities</li>
+          </ol>
+        </div>
+      </div>
+    </div>
+  );
+};
+
+export default APP;

frontend/src/__tests__/App.test.jsx

@@ -0,0 +1,109 @@
+import { render, screen, fireEvent, waitFor } from '@testing-library/react';
+import { vi, describe, test, expect, beforeEach } from 'vitest';
+import App from '../App';
+import apiService from '../services/api';
+
+// Mock MapLibre GL
+vi.mock('maplibre-gl', () => {
+  const mInstance = {
+    on: vi.fn(),
+    off: vi.fn(),
+    remove: vi.fn(),
+    addSource: vi.fn(),
+    removeSource: vi.fn(),
+    addLayer: vi.fn(),
+    removeLayer: vi.fn(),
+    getSource: vi.fn(() => ({ setData: vi.fn() })),
+    getLayer: vi.fn(),
+    setLayoutProperty: vi.fn(),
+    setStyle: vi.fn(),
+    flyTo: vi.fn(),
+    jumpTo: vi.fn(),
+    fitBounds: vi.fn(),
+    isStyleLoaded: vi.fn(() => true),
+    setSky: vi.fn(),
+    setTerrain: vi.fn(),
+  };
+  
+  return {
+    default: {
+      Map: vi.fn(() => mInstance),
+      Marker: vi.fn(() => ({
+        setLngLat: vi.fn().mockReturnThis(),
+        addTo: vi.fn().mockReturnThis(),
+        remove: vi.fn().mockReturnThis(),
+        getElement: vi.fn(() => {
+          const el = document.createElement('div');
+          // Add a simple way to trigger click for tests if needed
+          return el;
+        }),
+      })),
+      Popup: vi.fn(() => ({
+        setLngLat: vi.fn().mockReturnThis(),
+        setDOMContent: vi.fn().mockReturnThis(),
+        addTo: vi.fn().mockReturnThis(),
+        remove: vi.fn().mockReturnThis(),
+        on: vi.fn().mockReturnThis(),
+      })),
+      LngLatBounds: vi.fn(() => ({
+        extend: vi.fn().mockReturnThis(),
+      })),
+      MercatorCoordinate: {
+        fromLngLat: vi.fn(() => ({ x: 0, y: 0, z: 0 })),
+      }
+    }
+  };
+});
+
+// Mock apiService
+vi.mock('../services/api', () => ({
+  default: {
+    getLineOfSight: vi.fn(),
+    healthCheck: vi.fn(),
+  }
+}));
+
+describe('App Component', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  test('renders the application title', () => {
+    render(<App />);
+    expect(screen.getByText(/Line of Sight Settings/i)).toBeInTheDocument();
+  });
+
+  test('renders initial controls', () => {
+    render(<App />);
+    // Use role or more specific text to avoid duplicates
+    expect(screen.getByText(/Direction \(0-360°\):/i)).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /Show Line of Sight/i })).toBeInTheDocument();
+  });
+
+  test('calls API when clicking "Show Line of Sight"', async () => {
+    apiService.getLineOfSight.mockResolvedValue({
+      data: {
+        success: true,
+        data: {
+          conurbations: [],
+          line_coordinates: [{ lat: 0, lon: 0 }]
+        }
+      }
+    });
+
+    render(<App />);
+    const button = screen.getByRole('button', { name: /Show Line of Sight/i });
+    fireEvent.click(button);
+
+    await waitFor(() => {
+      expect(apiService.getLineOfSight).toHaveBeenCalled();
+    });
+  });
+
+  test('toggles map style', () => {
+    render(<App />);
+    const darkButton = screen.getByRole('button', { name: /Dark/i });
+    fireEvent.click(darkButton);
+    expect(darkButton).toHaveClass('active-style');
+  });
+});

frontend/src/services/api.js

@@ -1,6 +1,6 @@
 import axios from 'axios';
 
-const API_BASE_URL = process.env.REACT_APP_API_URL || 'http://localhost:3001/api';
+const API_BASE_URL = import.meta.env.VITE_API_URL || 'http://localhost:3001/api';
 
 const api = axios.create({
   baseURL: API_BASE_URL,

frontend/src/setupTests.js

@@ -0,0 +1,4 @@
+import '@testing-library/jest-dom';
+import { vi } from 'vitest';
+
+// Global mocks if needed

frontend/src/styles/App.css

@@ -3,6 +3,7 @@
   height: 100vh;
   width: 100vw;
   overflow: hidden;
+  position: relative;
 }
 
 .map-container {
@@ -19,6 +20,7 @@
   box-shadow: -2px 0 10px rgba(0,0,0,0.1);
   overflow-y: auto;
   z-index: 2;
+  position: relative;
 }
 
 .control-group {
@@ -62,6 +64,7 @@
 .setting-row span {
   font-weight: bold;
   color: #2c3e50;
+  min-width: 40px;
 }
 
 .setting-row button {
@@ -78,6 +81,12 @@
   background: #e9ecef;
 }
 
+.setting-row button.active-style {
+  background: #34495e;
+  color: white;
+  border-color: #2c3e50;
+}
+
 .action-btn {
   width: 100%;
   padding: 12px;
@@ -101,18 +110,66 @@
   cursor: not-allowed;
 }
 
+.action-btn-secondary {
+  width: 100%;
+  padding: 12px;
+  background: #34495e;
+  color: white;
+  border: none;
+  border-radius: 6px;
+  font-size: 16px;
+  font-weight: bold;
+  cursor: pointer;
+  transition: background 0.3s;
+  margin-top: 10px;
+}
+
+.action-btn-secondary:hover {
+  background: #2c3e50;
+}
+
+.disabled-controls {
+  opacity: 0.8;
+}
+
+.disabled-controls input {
+  pointer-events: none;
+  cursor: not-allowed;
+}
+
+/* Allow action buttons and settings buttons to work even when locked */
+.action-btn, .action-btn-secondary, .setting-row button {
+  pointer-events: auto !important;
+}
+
+.results-panel table thead {
+  position: sticky;
+  top: 0;
+  z-index: 1;
+}
+
 .results-panel {
   background: #f8f9fa;
   padding: 15px;
   border-radius: 8px;
   margin-bottom: 20px;
+  max-height: 450px;
+  overflow-y: auto;
+  border: 1px solid #eee;
 }
 
 .results-panel h3 {
   margin-top: 0;
   color: #2c3e50;
   font-size: 16px;
-  margin-bottom: 15px;
+  margin-bottom: 5px;
+}
+
+.results-panel .hint {
+  font-size: 11px;
+  color: #7f8c8d;
+  margin-bottom: 10px;
+  font-style: italic;
 }
 
 .results-panel table {
@@ -124,21 +181,114 @@
 .results-panel th {
   background: #34495e;
   color: white;
-  padding: 10px;
+  padding: 8px 4px;
   text-align: left;
 }
 
 .results-panel td {
-  padding: 8px;
+  padding: 8px 4px;
   border-bottom: 1px solid #ddd;
+  cursor: pointer;
 }
 
 .results-panel tr:nth-child(even) {
-  background: #f8f9fa;
+  background: #fdfdfd;
 }
 
 .results-panel tr:hover {
-  background: #e9ecef;
+  background: #ecf0f1;
+}
+
+.results-panel tr.selected-row {
+  background: #d5e8d4 !important;
+  font-weight: bold;
+}
+
+.info-panel-modal {
+  position: absolute;
+  top: 20px;
+  left: 20px;
+  width: 280px;
+  background: white;
+  border-radius: 8px;
+  box-shadow: 0 4px 15px rgba(0,0,0,0.3);
+  z-index: 1000;
+  animation: slideIn 0.3s ease-out;
+}
+
+@keyframes slideIn {
+  from { opacity: 0; transform: translateX(-20px); }
+  to { opacity: 1; transform: translateX(0); }
+}
+
+.info-panel-content {
+  padding: 20px;
+  position: relative;
+}
+
+.info-panel-content h2 {
+  margin-top: 0;
+  margin-bottom: 15px;
+  font-size: 18px;
+  color: #2c3e50;
+  border-bottom: 2px solid #4CAF50;
+  padding-bottom: 8px;
+}
+
+.close-btn {
+  position: absolute;
+  top: 10px;
+  right: 10px;
+  background: none;
+  border: none;
+  font-size: 24px;
+  cursor: pointer;
+  color: #95a5a6;
+}
+
+.close-btn:hover {
+  color: #34495e;
+}
+
+.info-grid {
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+  margin-bottom: 20px;
+}
+
+.info-item {
+  display: flex;
+  flex-direction: column;
+}
+
+.info-item label {
+  font-size: 11px;
+  color: #7f8c8d;
+  text-transform: uppercase;
+  letter-spacing: 0.5px;
+}
+
+.info-item span {
+  font-size: 14px;
+  color: #2c3e50;
+  font-weight: 500;
+}
+
+.action-btn-small {
+  width: 100%;
+  padding: 8px;
+  background: #3498db;
+  color: white;
+  border: none;
+  border-radius: 4px;
+  font-size: 14px;
+  cursor: pointer;
+  transition: background 0.2s;
+}
+
+.action-btn-small:hover {
+  background: #2980b9;
 }
 
 .more-info {
@@ -177,6 +327,25 @@
   flex-direction: column;
   align-items: center;
   font-family: sans-serif;
+  z-index: 100;
+  cursor: pointer;
+  pointer-events: auto !important;
+}
+
+.marker-number {
+  background: #2c3e50;
+  color: white;
+  width: 18px;
+  height: 18px;
+  border-radius: 50%;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  font-size: 10px;
+  font-weight: bold;
+  margin-bottom: -4px;
+  border: 1px solid white;
+  z-index: 2;
 }
 
 .marker-dot {
@@ -186,6 +355,7 @@
   border: 2px solid white;
   border-radius: 50%;
   box-shadow: 0 2px 4px rgba(0,0,0,0.3);
+  z-index: 1;
 }
 
 .marker-label {
@@ -209,6 +379,38 @@
   white-space: nowrap;
 }
 
+.map-info-popup {
+  padding: 5px;
+  font-family: sans-serif;
+}
+
+.popup-header {
+  border-bottom: 1px solid #eee;
+  padding-bottom: 5px;
+  margin-bottom: 5px;
+  color: #2c3e50;
+  font-size: 14px;
+}
+
+.popup-body {
+  font-size: 12px;
+  color: #666;
+}
+
+.popup-body p {
+  margin: 3px 0;
+}
+
+.maplibregl-popup {
+  z-index: 2000 !important;
+}
+
+.maplibregl-popup-content {
+  border-radius: 8px !important;
+  box-shadow: 0 4px 15px rgba(0,0,0,0.3) !important;
+  padding: 15px !important;
+}
+
 @media (max-width: 768px) {
   .app-container {
     flex-direction: column;
@@ -223,4 +425,12 @@
   .map-container {
     height: 60vh;
   }
+
+  .info-panel-modal {
+    left: 10px;
+    right: 10px;
+    width: auto;
+    bottom: 20px;
+    top: auto;
+  }
 }

frontend/test-results/.last-run.json

@@ -0,0 +1,4 @@
+{
+  "status": "passed",
+  "failedTests": []
+}

frontend/vite.config.js

@@ -0,0 +1,25 @@
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    globals: true,
+    environment: 'happy-dom',
+    setupFiles: ['./src/setupTests.js'],
+    exclude: ['**/e2e/**', '**/node_modules/**'],
+  },
+  server: {
+    port: 3050,
+    host: '0.0.0.0',
+  },
+  build: {
+    outDir: 'build',
+    target: 'esnext',
+  },
+  optimizeDeps: {
+    esbuildOptions: {
+      target: 'esnext',
+    },
+  },
+});