Ok so ... first thoughts .... "I guess you're not meant to reach level 6" ..... when you says the balancing isn't perfected I think that was the understatement of the year. It goes from easy, hmm yeah, to oh ehm what .... then the WTF?!?!?! Haha.
Nice tower defence concept. Assets are not exactly polished but I guess you're no animator :) The game mechanics work exactly as intended though. So for that I have decided to rate this as 2.5 / 5.
The game itself (as in all tower defence games) is nice to play and fun. The game is severely unbalanced and needs correcting before I could really rate this properly but given the authors programming background (and empathising with that slightly) I have to give this a 2.5 just for the fact that it works, it's playable and although not aesthetically pleasing ..... it does what it says on the tin.
Well played fella.