Render earth.png as a non-tiling feature sprite in the moon sky,
drawn between the far starfield and near crater terrain layers.
Introduce ParallaxFeature struct for single-instance background
sprites that scroll with the camera but never tile. Clean up the
feature reference in parallax_free to prevent stale pointers
between level transitions.
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.