could use keyboard short cuts and some other things to reduce the amount of mouse movements when dropping gems on a tower.
Since wave 100 or so - the game runs really slugglishly and has been consuming a processor core and several hundred megs of ram. Something to make it still function when you have a few hundred towers would be cool.
this has potential... but needs a save function, a score function that works, a difficulty setting (other than time consuming its not hard), and perhaps some way to get structures past level 9... whats up with that.