Fun..
Wow. This game is lots of fun to play, although i must say it does get boring after a while - not to mention repetitive. Yes, this does very much resemble Defend your Castle, and i like that, both are good games.
Somethings you should do to make your game more fun:
- Add more variety of sounds (dont always have the same gun shooting sound, randomize it maybe) aswell add a reload sound.
- I didnt get very far, but maybe have a little more variety in enemies.
- Maybe add weapon upgrades and ammo limitations.
- Perhaps allow to "degrade" from a current upgrade.
- A little more customization?
But great game!!! Good job.