I was able to beat Cosmo in the mid 90s. The choppy scrolling was a bit annoying when you knew that earlier PC games (e.g. Commander Keen Secret of the Oracle) and systems (hell, even the NES) could do way better. But still, at least this wasn't slowdown, the game ran just fine and was reacting quick to your inputs, just as it should. Plus, having parallax scrolling in a DOS game at all was mindblowing, and I did not realize until today that Cosmo ran in 16 color EGA mode - to me as a kid it must have looked like rather 256 color VGA instead. But then, both Keen SotO and Cosmo did some nice spritework and level design to hide their EGA limitations.