decent but bad graphics

graphics: 2/5 because your graphics may be home made but they lack the pizzaz that makes this kind of game awesome. in version two, if its coming, work on this area most heavily. check out these games for examples of what i mean. emphasis in "turret defence" "omega tower defence" and "canyon defence" work hard with this and it'll look great. for instance, make flashes when each turret fires. additionally, try changing the colors of turrets when upgraded. or make the enemies more than just a circle with a line down the side.

sound: 3/5 for effort. good job for making some sounds, but they are basic and obviously copied from the default sound collection. this site has lots of free sounds to use and it's free to join. try it out. and add some variety to the songs you have.

gameplay: amazing. great job dude, this game gets super frantic. it's pretty epic. i would appreciate making the later enemies give more money, though.

story: cmon dude! you're defending the last stronghold from zombie incursions! you're preparing to invade and they attack you! find SOMETHING!

interface: it's great, no worries. uh, maybe add "poof" when the turret gets upgraded.