The difficulty needs to keep increasing into the later levels. For instance right now I'm at level 300+ and they're still just sending groups of 5-8 guys for the majority of the time. I think either Blitz waves should start coming more often, or that things like jeeps, and then tanks, should start coming on normal waves rather than solely on blitz waves.
It's a decent concept, but after a certain point instead of getting more difficult it just starts becoming more and more time consuming. I think instead of having the puzzles increase in size, you should add new puzzle pieces (diagonal lines perhaps?) or something similar. 3/5.
Is it really necessary to have that same "guide" posted 5 times on every single page of comments? Please stop posting it so much-at this point it's no better than spam...
Maybe, instead of a save function, a checkpoint system would be better? For instance, if you lost, you would simply restart at the previous checkpoint with the same things you had then. There could be checkpoints every 10 levels or so.
So that way, for instance, if you do really well in the first 20, and then have terrible luck after 20, you won't need to restart the entire game.
I think the two hard badges should simply be combined into a single impossible badge. It'd be the same amount of points, but an impossible badge would be a more satisfying reward.
You definitely get faster. The changes between individual levels aren't particularly easy to notice, but you certainly can see the difference if you try.
 "Mud and Blood 2"){kind=icon}
 "Warlords: Heroes"){kind=icon}
 "loops of zen"){kind=icon}
 "The Necronomicon"){kind=icon}
 "light-Bot"){kind=icon}
 "Fantastic Contraption"){kind=icon}
 "Aether"){kind=icon}
 "Mercenaries 2: World Nearly In Flames."){kind=icon}
 "Ultimate Defense 2"){kind=icon}
 "Boombot"){kind=icon}
 "ZunderFury"){kind=icon}
 "intrusion"){kind=icon}
 "Pandemic 2"){kind=icon}
 "Ring Pass Not"){kind=icon}
 "Papa's Pizzeria"){kind=icon}