I played the game for the badge, but i love AI robot game.
Here the AI is totally dumb, but you can control the robot... which is a kill fun since the control sucks making the robots awful to control.
I felt frustrated and gave up at the 5th arena (pretty doable but the awful gameplay kill the fun too much)
Kingdom rush like in a MMO very expensive game.
You need to pay with kreds for almost everything, if you don't, you lose a loooooottt of time, because you even need to pay for speed up or skip button.
I played till lvl 19 then i found the game way too boring and stopped.