opsu! is an unofficial open-source client for the rhythm game osu!. It is written in Java using Slick2D and LWJGL, wrappers around the OpenGL and OpenAL libraries.

opsu! runs on Windows, OS X, and Linux platforms. A libGDX port additionally supports Android devices.

Precompiled binaries for opsu! can be found on the releases page, with the latest builds at the top. APK releases can be found here.

The Java Runtime Environment (JRE) must be installed in order to run opsu!. The download page is located here.

opsu! requires beatmaps to run, which are available for download on the osu! website and mirror sites such as osu!Mirror and Bloodcat. Beatmaps can also be downloaded directly through opsu! in the downloads menu.

If osu! is already installed, this application will attempt to load beatmaps directly from the osu! program folder. Otherwise, place beatmaps in the generated Songs folder or set the "BeatmapDirectory" value in the generated configuration file to the path of the root beatmap directory.

Note that beatmaps are typically delivered as OSZ files. These can be extracted with any ZIP tool, and opsu! will automatically extract them into the beatmap folder if placed in the SongPacks directory.

The "Music Offset" value will likely need to be adjusted when playing for the first time, or whenever hit objects are out of sync with the music. This and other game options can be accessed by clicking the "Other Options" button in the song menu.

The following files and folders will be created by opsu! as needed:

• .opsu.cfg: The configuration file. Most (but not all) of the settings can be changed through the options menu.
• .opsu.db: The beatmap cache database.
• .opsu_scores.db: The scores database.
• .opsu.log: The error log. All critical errors displayed in-game are also logged to this file, and other warnings not shown are logged as well.
• Songs/: The beatmap directory (not used if an osu! installation is detected). The parser searches all of its subdirectories for .osu files to load.
• SongPacks/: The beatmap pack directory. The unpacker extracts all .osz files within this directory to the beatmap directory.
• Skins/: The skins directory. Each skin must be placed in a folder within this directory. Any game resource (in res/) can be skinned by placing a file with the same name in a skin folder. Skins can be selected in the options menu.
• Screenshots/: The screenshot directory. Screenshots can be taken by pressing the F12 key.
• Replays/: The replay directory. Replays of each completed game are saved as .osr files, and can be viewed at a later time or shared with others.
• ReplayImport/: The replay import directory. The importer moves all .osr files within this directory to the replay directory and saves the scores in the scores database. Replays can be imported from osu! as well as opsu!.

opsu! is distributed as both a Maven and Gradle project.

Maven builds are built to the target directory.

• To run the project, execute the Maven goal compile.
• To create a single executable jar, execute the Maven goal package -Djar. This will compile a jar to target/opsu-${version}.jar with the libraries, resources and natives packed inside the jar.

Gradle builds are built to the build directory.

• To run the project, execute the Gradle task run.
• To create a single executable jar, execute the Gradle task jar. This will compile a jar to build/libs/opsu-${version}.jar with the libraries, resources and natives packed inside the jar.

This software was created by Jeffrey Han (@itdelatrisu). All game concepts and designs are based on work by osu! developer Dean Herbert. Other credits can be found here.

This software is licensed under GNU GPL version 3. You can find the full text of the license here.