The free-to-play games.
Play this mind-altering game and see if you can make it into the high scores. If you need practice on a certain level, just start another game from the title screen, and you can continue from any level, up to the highest one you've reached. Also, you get serious bonus points if you complete a level perfectly. Good luck! You're going to need it if you get to level 10... https://www.newgrounds.com/portal/view/37611