McOsu is a free, open-source rhythm-game client built around osu!( standard) beatmaps, with practice and gameplay customisation at its centre. It is developed separately from osu! and is not an official version or replacement. The design is aimed at players who already know the format: the game’s description notes that it does not provide gameplay tutorials.
Practice tools let players alter beatmap settings such as approach rate, circle size, overall difficulty and HP drain. A speed and BPM slider supports scrubbing through a beatmap, with quicksave and quickload controls for jumping to a point in its timeline. Players can also change mods and options during a run, while experimental choices include wobble, jigsaw, first-person play, flipped playfields and reversed sliders. The client includes live performance-point stats and an end-of-run ranking screen, plus VR and first-person 3D modes.
McOsu supports offline profiles with separate performance-point rankings, and its Workshop support covers skins. It can load beatmaps from an installed osu!( stable) setup or use custom paths; the description also says the client can run without osu!( stable), though that is not recommended.
