Needs polishing for certain - Make the graphics a little slicker, maybe speed it up to make it more challenging.. Like bullets are in other such games.
But you probably don't intend to work hard on this one. o:
very well done
... I did encounter a bug though... the pop up that says "Research Mines.... You need more Money $400" remains on screen even after the wave begins and then never goes away... it's distracting...
This ought to be easy to fix and beyond that I found it a cute little game and consider it well done.