As Iron Man, you'll have to join the Avengers and save the world in Iron Man: Rise of Ultron.
The right and left button keys let you move Iron Man. If Ultron wants to attack you, his target will turn red before the strike. Unsurprisingly, this means you need to move away from the targets to avoid Ultron's rockets. Also, get as many Iron Man coins as you can because they give you extra health.
The goal is to stay alive as long as possible while Ultron attacks you over and over again. The more you play, the more often and stronger the attacks will get.
Have fun and good luck!
