可行走跳跃的低多边形山羊小岛，Three.js 制作

Build a small interactive 3D island toy in a single self-contained HTML file using Three.js. The island is low-poly: a grassy hill with swaying grass blades, stylized pine trees, bushes, boulders, a fallen log, a low stone wall and a sandy shore surrounded by calm water under a pale sky. Place a controllable pet goat on the island. The goat walks with WASD, can sprint with Shift, jumps with Space, and climbs or hops up onto rocks, walls and other obstacles instead of clipping through them, with simple leg animation. Add an orbiting third-person camera that follows the goat, with drag to orbit and mouse wheel to zoom, and a small on-screen hint line listing the controls. Use soft daylight, gentle shadows and a muted green, grey and blue palette. Done means the goat moves smoothly around the whole island, reacts to terrain height and obstacles, and the scene runs at a steady frame rate in a desktop browser.