Return-to-Sport Hop Test: Limb Symmetry Simulator (2D)

This is the 2D-native counterpart to the 3D return-to-sport hop-test simulator. Rather than orbiting a rendered athlete figure hopping down a track, it draws the physics that actually determines the clinical outcome directly as two 2D diagrams: a true side-view parabolic trajectory plotted from the closed-form projectile-range equation, with every past trial marked at its landing distance, and a landing ground-reaction-force curve derived from the same impulse-momentum model as the 3D version. Tune the injured leg's quadriceps strength deficit, how softly it lands, and how long the push-off lasts, run a hop trial on each leg, and drag or scroll to pan and zoom the trajectory view. Live readouts track hop distance, takeoff velocity, peak landing ground-reaction force and knee-valgus risk for every trial, while the Limb Symmetry Index compares the two legs against the 90% threshold clinicians actually use to decide whether an athlete is ready to return to play.