This was probably about 10 minutes in:

[19:02:25] <GreaseMonkey> ok i’m just messing around with z80 assembler and meka
[19:02:35] <GreaseMonkey> (meka is a sega master system emulator)
[19:02:42] <Sparky> Oh, neat.
[19:02:46] <GreaseMonkey> it’s actually quite easy to load registers, palette and tiles

And now I’ve done my practice game at about 22:32. That took, ooh, 3 and a half hours to make a little not quite completeable one-level game?

Download here.

EDIT: Source code.