COOL!!! I've found a very fun game called the world's hardest game and it is very challenging but fun.
You can find the game here on this link: World's Hardest Game but this is how it works:
You have to use the arrow keys to move your little red square and have to make it to the other green patch. On some levels you have to only just try and get to the green part but on most of them you have to collect the yellow circles but you cant get hit by the blue circles.
You have to be really fast not to get hit and must have good reflexes, if not then it will take you longer to achieve a level. I like this game because it is really challenging and fast. Also because you have to try and get as less deaths as possible. There some levels like level 10 that is impossible to do. I give this game a rating of 7/10 because it's kind of hard when you go to higher levels. I have gone up to level 10/11 it is really hard.