Me thinks that you should really put a readme in the latest zip

I actually wrote a readme this morning, but I am too lazy to update the zip just for that
So yeah, you'll have to wait for the next release (which should come quick if I manage to solve that one problem I am facing...).

What's the problem?

"Clipping" rectangles. Axe's Rect clips, but when your rectangle is "far", its coordinates seem to loop and it's back on screen when it shouldn't. And so far, with all attempts I made, I either managed to never have rectangles that shouldn't be here but missing rectangles sometimes, or always have rectangles that should be here but supernumerary rectangles too -.-

Is that why the floor disappears sometimes?

Is it just wrapping byte boundaries? It sounds like you need to do some early clipping with your rectangles (check for overflow while calculating the rectangle coordinates). Hope you figure it out soon

"[Hayleia] and a few other programmers "
Hayleia can multiply

Not the only mistake they made :

• "for monochrome z80 calculators (the TI-83 and TI-84 being the most ubiquitous of these)". No 83, and what's the 84 ? I know a lot of calcs starting with "84" but I don't know any finishing with "84".
• "The game runs in 6 MHz mode with a simple background, or it can run in 15 MHz mode with a more complicated background". Where is there a background ? And it always run, whatever map you choose, just slower on 6MHz and only bearable on simple maps.
• "Right now both players need to play on the same calculator (with different keys)". Nope, two calcs work too.
• "and Fox is the only playable character". One can say Falco is there too or that no one is there since no one is finished, but "Fox is the only playable character" is false in both cases.

edit
I obviously don't complain about visibility and I thank websites who relayed the info, but it's better if that doesn't bring people on that topic to be disappointed to know that it doesn't run on their 83 for example.

Yes and no. The code for the game in itself is all from me. Then, ok, it's true that without a lot of people, I would have done nothing. You worked for sprites, Runer worked for Axe, TI wrote the TI-OS, ...
So yeah, I have a lot of people to thank but I wouldn't say we were a team working full time on this or something (even though, once again, I still admit that without you, my game would not exist).

Yeah, I didn't mean you worked drawing sprites, but you worked for sprite drawing