Lots of gameplay issues with this game. If youre either playing casually or for medals I recommend not to because of these issues.
The upgrading barely even upgrades anything. Your cloud shot cooldown is still slow, lightning (press s) starts empty and builds up and has a delay when its full. The baby dies almost instantly when 2 or more enemies hit it even at full upgrade. Upgrades are only worth it to get the extra abilities and for your own health.
The goblin instantly teleports on top of you which is complete bs when your already getting swarmed by enemies.
The kamikazee enemy will almost always kill the baby in 1 hit if it touches it.
The difficulty increases by 1 enemy each level so basically youre playing the final level 5 times when you get to the end.
If you get swarmed and try to save the baby by running through enemies, dont, you'll die immediately, enemies dont even have to touch you to hit you.
Using the mouse to choose levels and upgrades is annoying because you mostly play with keyboard anyway.
If youre still gonna play for medals (180 points) my tip is to play the first level repeatedly until you upgrade as much as possible and when you get to the tough levels drop a barrier on the strong side (most enemies) fight the horde from the other side until you can use lightning and then use barriers and pick off the remaining enemies, this is the only thing that worked for me and even then its tough because the designer made it so a large horde hits you a bit before your lightning charges so you'll have to fight just to stay alive before you can even use it. You also get 0 drops on the final level so be prepared if youve been relying on them up until then.
One more thing if you want the 30 gem medal dont upgrade at all just get it otherwise you'll be stuck grinding at the end it took me two hours to finally get all the medals and to activate them you need to go in and out of the shop a few times.