You lose! Have I ever started?!
It's impossible to win (if you expect a standard TD), just too many enemies in the same moment, and no prevoius instruction. Try to add a tutorial, there's also a bug, if you lose, but you don't press "Ok" you can still play, at least you can put towers in price order (the first time I started with Fire and Ice tower, and I soon found myself without money and towers). Also I like the idea of levels (even though it isn't new), but I think it could be more enjoyable by adding a story (this could be a good way to add a tutorial). Hope I'll see the new version, but there's a lot of work. Good luck.