osu!

osu! is a free-to-play online rhythm game
osu! gameplay is based on a variety of popular commercial rhythm games. While keeping some authentic elements, osu! adds huge customisation via skins/beatmaps/storyboarding, online rankings, multiplayer and boasts a community with over 500,000 active users! Play the way you want to play, with your own music, and share your creations with others.

Game levels are called beatmaps. In each beatmap, a song will play and different rhythmic hit elements (hit circles, sliders and spinners) will appear on the play field. Players must use a pointing device to manipulate these elements in time with the playing song's rhythm in order to earn points. The use of a graphics tablet in combination with a keyboard is common in osu!, although some players do use a mouse.