Pretty good game, but much to ease i think. You could give more challenges to do than 27. I found totally useless to upgrade armor, health and emp.
Gun Cannon or spread should work in other way because after 3 upgrades its pretty imba to just spam click to have very big firepower. Its should be % chance to have more shoots than just first. I don't know if investing in more cash gain upgrade was even worth to do. After 50 wave i had enough nothing interesting and not much of challenge, not enough cash gain to have my attention for maxing stuff.
Overall too ease, need more chalenges but humor was great.