I built this for a hackathon and it kind of blew up 1,300 players from 50+ countries in the first week with no marketing budget. The idea: what if Wii Sports ran in your browser and your webcam was the controller? How it works: Google's MediaPipe tracks 33 body landmarks from your webcam at 30fps. Those get mapped onto a 3D avatar in Three.js. A custom physics engine handles ball flight with gravity, air drag, and Magnus force for spin all calibrated against real professional match data from 689 Federer matches. The game detects forehand, backhand, serve, and slice purely from how you move your arm. No buttons, no keyboard, no gamepad. The hardest part wasn't the code it was the physics tuning. Single-camera depth estimation is noisy, and naive smoothing kills responsiveness during fast swings. Took days to get the One Euro Filter dialed in so it feels smooth at rest but snappy when you swing. What surprised me most: 60% of visitors actually play. Typical browser game conversion is 10-30%. Turns out removing every friction point (no download, no signup, no hardware) changes behavior dramatically. Would love for you to try it and tell me: does it feel like tennis? What shot did you try first? What broke?

LiveWebTennis

Swing your arm at your webcam to play 3D tennis in browser

Swing your arm at your webcam to play 3D tennis in browser