Make a 3D voxel sandbox game in one web page: an endless blocky world with forests, beaches, mountains, caves and water, generated from a seed. First person: WASD to move, mouse to look, Space to jump, left click to break a block, right click to place one, keys 1-6 to pick from a hotbar of block types. Add a day and night cycle with a sun and moon, clouds, soft lighting and ambient occlusion on blocks, falling leaves and block-break particles. Add a crosshair, hotbar HUD and a short how-to-play overlay that disappears when you start. It should feel fun the moment it loads.