This is a 2D companion to the 3D Kick Elephant simulator. Instead of a physics-engine sandbox with crates and an orbiting camera, it isolates the one real law the joke depends on: the impulse-momentum theorem plus Newton's third law.
- Impulse: J = F·Δt is the same for target and kicker — the foot and the target exert equal and opposite forces on each other for the same contact time.
- Velocity change: since J = Δp = m·Δv, the resulting Δv = J/m. A 4,000 kg elephant and a 70 kg kicker feel the same impulse, so the elephant's speed change is roughly 57× smaller than the kicker's — inertia, not "toughness", is why it barely moves.
- Projectile flight: once launched, the target follows real 2D projectile motion under the chosen gravity — range and hang time both scale with v² sin(2θ)/g.
- Kicker recoil: the kicker's reaction velocity is stopped by ground friction — a real kinematic slide, d = v²/(2·μ·g) — so a light kicker against a heavy target visibly skids backward while the target barely creeps forward.
Switch the target to Human or Mouse to see the ratio flip: kicking something lighter than yourself sends it flying while you barely feel the recoil.