Increase base fall speed (120→200), acceleration (200→350), and respawn
delay (3→6s). Add random horizontal drift (±60 px/s) so asteroids fall
at angles. Widen initial stagger (0-3→0-8s). Reduce moon level from 24
asteroids to 8, spread evenly across the level.
Distance-based sound effects with stereo panning for explosions, impacts,
and pickups. Spacecraft entity with full state machine (fly-in, land, take
off, fly-out), engine/synth sound loops, thruster particles, and PNG
spritesheet. Moon level intro defers player spawn until ship lands.
Also untrack build/ objects that were committed by mistake.
