程序化海岛上的穿门加速空中竞速游戏（Three.js）

Build a browser flying game with Three.js on a procedurally generated low-poly island. The player pilots a small jet in third person through a series of glowing gates scattered over hills, beaches and lakes, against a timer. Generate the terrain, pine trees, rocks and water in code. Add a start countdown, a HUD with elapsed time, gates passed out of fourteen, speed and a boost meter, plus a circular minimap in a corner. Boost should leave bright exhaust trails and speed lines, and the camera should follow smoothly with soft sky haze and gentle lighting. Use a calm green and teal palette. Deliver one self-contained HTML file with keyboard controls. Done means the island is flyable, gates register, and the HUD updates correctly.