Put on some music, click in time to the beat and create some generative art out of it.
Ok, so it's not actually a game, but it's an interesting use of Phaser all the same! Just start a piece of music playing (like in iTunes or from a stream) and then click on the interaction in time to the beat. You'll see it generate a nice pulsing wave of graphical effects, which shift around and move in time to your mouse clicks. It's all quite rhythmic!