... Suck.
Its freakin impossible to get trough the 1st lvl in the last round. The towers couldn't do enough damage to kill the fast guys. You really should do a Difficulty option since its not everyone who's pro in those kind of defence games. At least do the difficulty option then maybe more people will like it. Not to be rough but its true. Many people i know that played this game couldn't even pass the 1st lvl as i do. Another good thing you could do is a wave number so you can see where you are in the level.