Patrick Buckland's mouse-and-inertia arcade game — the first color game on the Macintosh. Collect every crystal, dodge the nasties pouring out of the side portals, and escape through the gate at the bottom. The mouse changes your velocity, not your position; stopping is the hard part. Needs a mouse.
Physics constants lifted from a disassembly of the original 68K binary: ship velocity = (mouse offset from neutral) ÷ 10, clamped to ±9 px per update at 30 updates a second on a 512×342 field; bullets fly at 4× ship velocity; 3 ships, 3 bombs; bonus ships every 15,000 points to wave 11, 40,000 to wave 26, 75,000 after. The walls never kill you. The gate posts always do.