1-D vertical free fall · constant g = 1.0×10⁻³ m/s² (67P surface, varies in reality) · no comet rotation, no gas drag · Earth panel neglects air resistance (stated!) · bounce modelled with a restitution coefficient · escape speed ≈ 0.9 m/s applies to the REBOUND velocity.

1️⃣ Watch — same drop on Earth & 67P, live
2️⃣ Predict — compute t & v; numbers unlock Release
3️⃣ Inverse — find the push v₀ for a target touchdown
4️⃣ Bounce Crisis — the real 2014 failure, your call
Bronze+ unlocks the next stage.

Space release · P pause · R reset stage · H hint · Enter commit. Each stage opens with a 🧠 reasoning question that unlocks the numbers. Wrong submissions −2 pts. ⏩ Time compression is always labelled — physics is never faked.

Every stage: answer the reasoning question, then compute and commit a number. Your medal is set by accuracy — 🥇 under 5% · 🥈 under 10% · 🥉 under 20% error — and a Bronze or better unlocks the next stage. A wrong answer costs −2 points (−1 on Easy, and your first reasoning slip on each question is free on Easy). A hint costs −3/−4/−5. Fewer tries and higher accuracy mean a higher score — so it always pays to calculate, not guess.