It's funny how many people can't figure this game out...
Every level beaten gives you experience. You use this experience to get unlock upgrades ON THE LEVEL SELECT SCREEN. When you start a battle you do not have anything unlocked. You must save your mana to unlock your upgrades. (Unfortunately, you cannot see how much mana the upgrades cost.)
I've found the easiest way to win a level is to only upgrade your mana amount (spacebar) until you get to a large maximum amount (2000 in easier levels; higher for harder levels) then buy your upgrades, wait for your mana to get back to max, then spam your units like crazy. It's fun to see your army of ~200 completely annihilate the opponent. :)
Why does no one like this? It's a great game!
The controls are challenging (they're meant to be!)
The gameplay is repetetive but in a fun way (has no one played galaga? pacman?)
and 1gnusrhus, your comment is the stupidest ever. The term "hard badge" means that its suppose to be challenging and it might take you more than 10 tries...
Whoa this looks like the billions of other flash games with the same concept...
1/5 for the music, pop-ups (wtf is up with that?), and lack of originality...