+1d!

The game looks a good bit clearer in the most recent screen shot. The first screen shot you posted didn't look this good (or smooth). So anyhow, the speed looks great. Not sure about the blurriness on calc, but it doesn't look too bad in the most recent screenie.

I think that's inevitable in Axe, though, especially in scrolling games.

By the way, why are you pushing (and pop after) all register at the begining of your interrupt routine ? That is useless, unless you use shadow register, wich I haven't saw in your code.

Since Runer112 helped me find this issue (which was due to the fact DispGraph^rr was slower than the interrupt frequency at speed 0 and disabled interrupts, so in fact, some frames were skipped while they shouldn't have been), I can now release a version using interrupts.

It is a bit slower but grey is constant (instead of popping when a new pipe is created behind the scenes).
Use Left/right in the calibration screen to choose a mode (choose the one where the grey is the less flickery of course) and +/- to change contrast (it will be set back to its initial value when quitting the game).

@JWinslow, unpause using 2nd too

edit No, it is not so difficult. I don't manage to get more than 13 in the screenshot but on real calc I reached 15.

This looks much nicer actually. Gonna have to try it on my calc to see how it looks like. Is the grayscale constant on each calc via some LCD driver auto-calibration btw? I remember some ASM game did that, but I don't know if Axe programs or axioms can.