for level 15 you need to bend the left laser firsr, and then split it. in level 17 you got one spare part ^^ last level was nice, but too easy compared to lvl 15 :P better make lvl 15 the last one :D
Bug: On wave 4 and 5 (didn't check further) the level stops after wave 23/24 (auto wave enabled)
Suggestion: Increase the difficulty a little.. At this moment I'm putting loads of machine towers at the spawn and I the "mobs" dont stand a chance
The inferno is a nice improvement on the game, but doing the same levels over again is no fun..
4/5 because of the play with gravity and the dynamic in the game.