Touch Target Fitts's Law Simulator

Mobile accessibility guidelines specify concrete minimum touch-target sizes — 44×44pt on iOS, 48×48dp on Android — but the reason those numbers exist is a well-studied piece of human motor control called Fitts's Law. This simulator renders a live grid of touch targets on a 3D phone mockup and repeatedly fires a simulated finger tap at a random target, computing the predicted movement time from Fitts's Law and landing with Gaussian aim error scaled by a motor-impairment slider standing in for a low-dexterity or tremor-affected user. Drag target size and spacing down and the hit rate collapses; switch on the WCAG minimum-size guide rings to see exactly where the iOS and Android platform thresholds sit relative to your current size, and watch throughput (bits/s), mean movement time and hit rate update live as you tune the layout toward — or away from — an accessible one.