that was a good time passer
it does last forever. i had 3 drones of each type at lvl 8 sitting on that red trench type thing, and got my laser dmg to around 35 b4 i called it quits. im not sure y ppl r complaining its too hard, its fine to me, they needa learn to point and click imo. interesting u have to be on the enemy to shoot him. i personally like the constant flow of enemies over the "round 1, 2, etc" regular style.
improve: i didnt rly like the caps on the upgrades... instead, just make them cost a lot more than usual per upgrade. maybe make a [save and quit] button, incase u wanna pass more time later. add some more upgrade types, such as a larger blast radius for the laser. Add a description when u mouse-over the buy button. key-bind the letter "P" or something for pause. i seen the pause button but thats a pain to get to when u needa new upgrade and there's 10 ppl hitting your base. Smart drones - tell them what not to shoot at. that way, they shoot small stuff and destroy it while u can handle bigger enemies.
very good game man, when's number 2 due?