I'm really enjoying the game but there is definitely a bug with objects persisting beyond use. With balloons it's really frustrating, with fuel cans it's a potential exploit. Also the top bar that appears during game play? I would either make it persistent or have it be accessible only through the main menu, sometimes it gets in my way and it breaks the flow of the game.
It would be nice to see some minor bonuses for achievements. Nothing huge, for example +10% starting gold, 2% reduction on barrack repop, 4% to atk spd for a certain tower, etc.
I thought TD was a worn out genre, then I came across this gem! This game is extremely well done and this is an excellent example of the difference between a game that's inspired versus just another rip-off. I especially like that the barracks give it a bit of a tactical angle, I'm actively involved in the strategy when the waves come rolling in.