I'll give credit to Valve, they continue to support their games far beyond the lifespan of most developers, and eight years after it's release, Portal 2 is still getting neat little additions and updates.
The update actually improves co-operative gameplay locally on PC, by allowing one player to use a controller and the other to use the keyboard and mouse . It might sound like something you'd have expected to be there all along, but before today, it actually wasn't possible without complicated workarounds.
It's probably related to Valve's new Remote Play Together functionality, so it makes sense they'd want to get Portal's co-op multiplayer in order. They've even added local co-op support on the community coop map queue.
The patch also adds a few more improvements, including fixing various bugs. The full patch notes are below;
- Fixed an issue where in-game audio caption language would use the system language setting instead of the Steam language setting.
- Improved camera control through Steam Input – the sensitivity scale has changed so you may need to increase your configuration’s sensitivity.
- Add local coop support for one controller player and one Mouse/Keyboard player.
- Add local coop support from the community coop map queue. Quickplay is still not supported.
- Fix XInput related options being hidden when connecting a Steam Input enabled controller using a Gamepad configuration.
- Fix the challenge mode screen not having enough footer buttons available through Steam Input.
- Fix several more bugs where the incorrect action set could be set in Steam Input.
- Fix several cases where having a controller connected but not active would affect the glyphs and settings screen options.