I would say make multiple floors with ladders or something, maybe doors with levers or some sort of action (spacebar?) to open, maybe something to collect. Very nice so far.Oh, and try to stick with one texture per area or floor.
Sorry about the 3 in a row, but in level 18, the lower blue plasma, if you jump while standing on it, you fall through. are you supposed to be able to do that?
Found but 1 glitch. In i think level 12 with the 3 spike barriers, i wentr through the exit and it spit me back out at the entrance of the level, no portals used.
If you go to the info screen then return to the title screen, the music starts overlapping, like playing the first time and a second time. check it out.
 "Take Something Literally"){kind=icon}
 "Frantic"){kind=icon}
 "Bloons Tower Defense 3"){kind=icon}
 "Horrible Quiz 2"){kind=icon}
 "Maze Test"){kind=icon}
 "Portal: The Flash Version"){kind=icon}
 "Precision"){kind=icon}
 "Midnight Demo"){kind=icon}
 "Dark Cut 2"){kind=icon}
 "Micro Olympics"){kind=icon}
 "More Mindless Violence"){kind=icon}