Hi,
I've been working on tools for a new 8-Bit computer, the Cerberus2080, which has both a Z80 and 6502 processor (some details here: https://www.thebyteattic.com/p/cerberus-2080.html )
As part of this, I've developed an online IDE and emulator, and have used it to write a Manic Miner style engine for the computer in 6502 assembler.
The code is written from scratch, with the level data using my own fairly efficient format (about 350 bytes/level, sprites are stored without mirroring). So far I have the first couple of levels working (no vertical guardians yet!) and I think it's fairly accurate to the original. You can see the source code and try it out in the emulator here (Chrome or Edge browser required):
https://feertech.com/legion/cerberus.html?p=miner/rtz/&f=miner.asm,utils.asm,sprites.asm,graphics.asm,level1.asm,level2.asm
I'd be very grateful for any feedback.