This is such a great idle clicker. Definitely my favorite so far. I think the graphics have a big part, they remind me a lot of Advance Wars. Thanks for the update!
Found a bug: I you leave some of the level 1 invaders on the screen and earn enough to have the level 5 invaders appear, the level 1 invaders will be frozen on the screen and not disappear when clicked.
 "Save the Earth! - The Incremental -"){kind=icon}
 "Hook"){kind=icon}
Thanks for reporting, that's fixed in the next update.