Osu! has been one of my favorite Games since ever so I thought I share the Joy and tell you about Osu!.
Osu! is a Rhythm Game where you have to hit circles that appear on screen with your Mouse. Theres also Spinners and Sliders. Spinners you have to rotate the mouse around like crazy to "hit" it. And Sliders start out as normal Circles and then you have to follow their Track with your Mouse. All that happens playing a Song in the Background but you can´t just use your own songs. On the Osu! Website there is a Section called Beatmaps which are pretty much the Songs that were made into Maps for Osu!. That pretty much covers it and since I´m really bad at explaining things I recorded me playing a Beatmap in Osu!. The Song is Reach out to the Truth (Instrumental) from Persona 4:    
http://www.youtube.com/watch?v=dXiqVDwrkao          
So if your bored, go ahead and download Osu! here: 
http://osu.ppy.sh/p/download. Don´t forget to register or else you can´t download Beatmaps. 
 
Have Fun!