PaddleLab XR

an AR/VR table tennis coach built at Hack the North 2026. it runs straight in the browser through WebXR, so on a Meta Quest 3S you just open the url and you're at the table. no app store, no sideloading.

the ball runs on a small custom physics engine rather than an off-the-shelf one. it's a regulation 2.7 g ball with quadratic drag, Magnus force so topspin dips and backspin floats, spin-aware bounces off the table and paddle, and swept collision detection so a fast swing can't tunnel straight through the ball between frames.

every way of holding a paddle feeds the same paddle object: Quest controllers, Quest hand tracking, mouse and keyboard, webcam hand tracking through MediaPipe, a real paddle with printed ArUco markers on it, or a phone used as the paddle with its orientation sensors and haptics. physics, rendering, and scoring never know which one you're using.

versus mode is one simulation, one host. the hosting device runs the physics and streams the ball at 30 Hz, and the other player only sends their paddle back. that keeps latency-sensitive round trips out of the rally. it syncs over a LAN relay, Supabase Realtime, or BroadcastChannel for two windows on the same machine, with room codes to join.

on top of that there are seven arcade drills (topspin drive, backspin push, flat block, sidespin mix, an infinite ball machine, target practice, and a rally against an AI), and a coach mode that scores your serves, drives, pushes, and blocks, gives per-shot feedback, writes a post-match breakdown, and reads it out loud.