The osu!(lazer) client logo.
"Lazer" is the code name for the next major update to osu!. While the other release streams are feature-locked, lazer will continue to receive updates and eventually become the new "stable" client, with other versions renamed accordingly.
Draft versions were uploaded on flyte's design blog starting from 2016.
Implementing the design and new planned features using stable's code base proved to be difficult or even nearly impossible due to technical debt. As such, work started on a complete rewrite of the client early 2016 and a first release was published on GitHub on 12 February 2017, containing a bare-minimum implementation of gameplay in the osu! game mode, and the new menu designs.
A game framework is concurrently maintained as a separate project, the osu!framework, which includes general, lower-level components and infrastructure that may be useful in other games or applications.