Brutally slow paced
The concept is ok, controls are good, gameplay is good.. but the pace of the game is way too slow, and the upgrades are backwards. When you get flooded by enemies in the later levels and have to use your special weapons, it burns all your energy and you can't shield anymore. You're better off just using the regular gun in 99% of situations, and the upgrades are either way too expensive, or you just don't get enough money. I got bored and quit after doing level 7 five times and I still couldn't afford a power upgrade.