(author here) "you'll notice the speed of the animation change" that might be, but the demo is designed to run at equal speed on all systems (it hooks into the timer) if you experience animation speed differences, that means your system can not handle what dosbox (on high cycles) demands. It should be noted that DosBox is far slower than people expect it to be, and also, that in actual competitions in the demoscene, real modern hardware is booted to Freedos, but has no sound. So if you want sound (with MIDI) in a competition, you have to stick to the rather slow dosbox, and even optimize against an emulator which can be really really weird. (https://www.pouet.net/topic.php?which=11881) I wouldn't claim the demo runs fine on a real 486, but a pentium should do, as a variation of the raycast tunnel part indicates (https://www.youtube.com/watch?v=5_3CU6shKlY)