Too repetetive...nice graphics, but it took way too long for a medium/easy badge... at least make it faster to earn points after you kill a certain number of enemies or something? And the final boss is way too easy to kill, since by then you already have all the upgrades..
Hard! But addicting..but REMOVE THE SHAKE FEATURE OR MAKE IT OPTIONAL PLEASE. Also the buildings are pointless, they may even harm you since you have to click on the icons to activate them all the time..