No, it's an NTSC release, and I have no idea how it would run on PAL. The only visual bug I know of is the fact that, once roughly every 90 seconds, the music loops and causes the driver to overshoot my next screen cut (I'm not using interrupts right now, but rather busywaiting until the desired scanline). I'm not sure how to overcome that. As you can tell, I'm calling the driver towards the middle of the screen, but even using the large area taken up by the logo, it would still overshoot my next screen cut. I don't want to convert to interrupts just yet - this is the same way I learned to code on the C64, by busywaiting, then I graduated to IRQs.
The "flickering" you're talking about is the rastertime counter for the music driver - I change the backdrop color before and after the music driver so I can see roughly how many scanlines it eats up. As you can see, it's fairly good in that it doesn't generally eat that many lines. At first I wasn't sure what you were talking about, as I had already removed this in my current build.
Yes, S1 refers to the hybrid 68k/Z80 driver found in Sonic 1.
