The mane tools are a cross compiler, a disk image creator, & an emulator.  It's purely intended for the 320x200 bitmap mode.

The preferred toochain is CC65.  That has an assembler & C compiler.  Apparently C is hopeless on the 6502.

https://cc65.github.io/

Disk images are created with c1541, which is part of the emulator.

https://codebase64.org/doku.php?id=base:tools_for_putting_files_into_a_.d64_image

The lion kingdom must confess to being more fascinated with commodore emulation 25 years ago than now that the rest of the world is.  All the demos seem to cut off after 2000, so retro computing might just be the gootube algorithm's own fabrication.