Osu! is a freeware rhythm game. Its game play is based on commercial titles including Osu! Tatakae! Ouendan, Elite Beat Agents, Taiko no Tatsujin, Beatmania IIDX, O2Jam, and DJMax. As the song plays, the player must click on different hit-elements (hit circles, sliders, and spinners) in time with the rhythm of the song in order to earn points. This is done using a mouse, although more experienced players tend to use other input devices such as a graphics tablet or touchscreen. (wikipedia.org)