Findings

What the other pages don't cover: two things the binary has and the game never uses.

There's room for two levels that don't exist

Background maps are located with 0x3000 + level * 0x200. There's space for eight, but only six have data: the 1024 bytes that levels 7 and 8 would occupy are 0xFF filler, and the loader stops at the sixth with a cp 6 / jp z,0xC000.

135 bytes that never execute

Four stretches of perfectly coherent Z80 that no path reaches. Among them, a full-screen colour effect that turns every black into transparent — 3673 of the screen's 6144 colour bytes — and which only makes sense paired with a change of backdrop colour. Half a fade that got left out.

The effect that was never used

The full story of all four is in DEAD-BYTES.md.