Quite personally i think the most important upgrades here are speed, reloading turning, and moving. Buying extra armour is fairly useless. But this is a god game, which is sometimes frustrating. 3/5.
I love this game for it's great mechanics, simple gameplay, and involving bossfights. Get it a badge! 5/5 for being everything it could be on its premise.
As always, respect to Ragdollsoft for their awesome games. This one is a nice, balanced mouse avoider that adds layers of complexity with the repulsion of balls against each other. 4/5.
Not a big fan of taking your chances on positioning and a main menu that seems to take 4 minutes to load. But it's nice and calming, well, not really, it's actually quite infuriating on later levels, but it is well made. 3/5 for being average.