could be better
i liked it it was entertaining but me get idea for better game:
1) you should make it so me is able to upgrade gun in differents ways like upgrade reload time, fire rate and stuff
2) guns should not be locked by your level. you should be able to buy them. it was frustrating at beginning i had lot of money but could not spent it on anything cuz i knew older guns were going to become useless later so it is pointless to spent maney on upgrading them
3) automatic stuff. my favorite strategy in any defense game is to buy automatic turrets or gunners or whatever is automatic.
4) game modes. yeah.... games modes....
5) storyline.
overall good stuff but there are so much defense game that if you want good rating you really need to do a wakzaucking good game