Tower Defense, survival mode, have fun!
Nvm I beat it without reading the tutorial. I'm going to describe the strategy I used here, so if you don't wanna know how to win, don't read any further. So first thing you want to do is save up and spawn as many archers as possible. Continue doing that until you are sure that your defenses will never ever be breached. Then start spawning mages. Repeat 1st 2 steps until you win.