Waaaay too easy. Fighting rounds gives you more ammo and health than buying it. Item pickups shouldn't drop after each death. There are way too many health and ammo packs.
The platforms are longer than they are actually shown. Also the game thinks that the head is the entire body, so if you hit a platform with your head you can double jump.
Too easy to upgrade everything, each upgrade is worth very little. It should be more specialized like should I go for more defense or speed. Also why the hell does the tank have to use hit and run tactics, its a freaking tank.
Movement Arrows should appear when you mouse over the character, or should always be active considering he is the only character you control. Aside from that, great game.