Looking at the description, this is just extreme hate on whole humanity. Paladog more like Misanthropy Simulator 2012. To the Game Developer: Are you alright? What went wrong? Honestly, good luck.
I was able to complete the game. Here's how I made it: the first 10 waves are easy (upgrade the bomb cooldown), the hard ones are between the 11th and 25th. Focus on few upgrades, I suggest these 4: bomb & health cooldowns, bullets spread & armor. Upgrade cooldowns to level 7/8 and the other two to level 5/6. Save money for props box and enemy freeze. When you have all "skills" available, upgrade everything, and the last 5 waves won't be hard, except the final boss, but with some luck you can make it. Damage upgrade is awful without capacity & spread bullets. Coins upgrade is awful, even level 6, so put little over it. Use freeze and bomb together. Also get the bonus coins. Last: then there's the moment you realize it's just a BIG rip-off of Berzerk's game Peacekeeper, just in a <> as the game description says. I have to say one thing to DragonGameStudio: inspiration ≠ copying
After you find all the 6 endings, go to the little house before the sheep's fence, and try open the door...it's strange that there are still sheeps in the fence and not humans, right?
Still counts as a PASSED exam :)