A 3D recreation of the Sans boss battle from Undertale, built with Three.js and rendered via WebGL. A player-controlled red heart moves within the battle box and dodges white bone projectiles spawned by the floating Sans character. Attack patterns include horizontal, vertical, circular, and random bone spawns, with collision detection reducing HP and triggering invulnerability frames. The code uses Three.js geometries for meshes, input via WASD/arrow keys, and a simple game-state manager for health and game-over logic.