Press space or click to shoot gun. Use arrow keys to move, and gun will point in the direction of mouse pointer. Don't touch the zombies. 6 WAVES For now.
Thanks for @SullySully for the tutorial TIP: In the second wave, the bullet powerups become almost mandatory to win. In the third wave the zombies become bigger, and that is when you have to run a lot. For the fourth wave, I'll leave you to see what beast is it.