The game suffers some balance flaws.
-The spellbooks are all relatively useless except for the first and the last one (Wich is also hilarious) I ended up avoiding the taromicon and the thunderomicon the whole game since they slow down the pace of the Gameplay a lot.
-The action is kind of messy, with all this stuff going on around the character we have trouble to see what is a bonus and what is a projectile.
-The fuel upgrade is relatively useless as if the player spams the screen hard enough he can hover in the air quite indefinitely without having to refill whatsoever
-The fact that you cant choose what kind of dude you want to buy first is infuriating and it feels forced, since they cant be desactivated, I ended up running mostly into fuel dudes who were no help at all.
-The spells are all relatively useless except for the sawblades and the Miskatonic, the later for obvious raison, the sawblades because with a maxed out rate of fire it is easy to just spam everything before it even enters the screen, and since this spell is relatively cheap It can be spammed easily and wipe out most of the foes before they even become a threat;
-The sawblade utility is also enhanced by a game breaking bug I found out, if you stand just in the center of the screen during the transition to a boss fight while this spell is on the boss will appear during the opening scene and die on the saw before the fights even begins. wich is useless against the final boss but allow the player to tear through the 2 previous boss without suffering damage.
-Having to unlock all the missions to finish the game is infuriating. True the missions are easy enough but it feels like the game is robbing the player of his victory when he get this far for the first time.
Apart from that the game is fun but as I said it's too bad that only 2 upgrades where truly interesting in kind of each section (Heart dude/Money dude - Sawblades/Miskatonic - Firemicon/Tentamicon) and the rest of the poorer updates are mandatory.