Ah yes, the enemy for sure needs a reason to attack, something that we completely overlooked ":D Having something to defend seems like a nice idea. Guess we gotta borrow some elements from the tower-defense genre. Diverse player units with upgrades for both player units and enemy would be a great addition. "Lots of bullets." Love the sound of that :D Multiple maps would be a great addition as well. The suggestion about income generation is also interesting, I'm thinking there should be some more factors affecting it along with the ones you mentioned. Thanks a lot for all the great suggestions. Really appreciate it :)