Computers may be dumb at playing games without any algorithm. But it is possible to make a powerful gamer out of a computer using machine learning. Take MarI/O for instance. It is a smart program that learned how to play Super Mario like a pro from scratch. It did so using an approach called neural evolution.
MarI/O started as a dumb player but as it went through the learning process, it figured out how to play the game. It took the program several tries to improve. The developer used the NEAT algorithm to accomplish this. Watch the above video to get a better idea how MarI/O works.