I get a black screen after every level, either before or after the upgrade screen. The score is saved though, so with a reload I can keep playing, but it's a big inconvenience anyway. Otherwise it's a fun game, for a while, with the insane amounts of points required for each upgrade it's a bit discouraging for longterm play. I like the idea though, if it was rewarding enough the endlessness wouldn't be a problem. Keep it going!
-cd-