Heh, I once made a level with bouncy-pups spawning, and I let my PC run while having a pencil on my space key. I had 50k ammo or so :P
As for the lighting: though there are waves, there aren't as many as in the current version I think, so maybe the lightning was possible then, and, lightning combined with more waves, it's probably the problem with what LRK said: PCs of those days.