ld bc, Tiles.end - Tiles sets bc to the length of the tile data: Tiles.end is the address of the first byte after the tile data, so subtracting Tiles to that yields the length.
Tiles.end should probably be TilesEnd. I couldn't find this source in this repository so I wasn't able to submit a PR.
From https://eldred.fr/gb-asm-tutorial-v2/part1/jumps.html#conditional-jumps:
Tiles.end
should probably beTilesEnd
. I couldn't find this source in this repository so I wasn't able to submit a PR.