An update has been released for Portal 2.

Improvements:
  - Implemented a Vulkan render backend (currently accessible through the -vulkan command line parameter).
  - Improved compile time for Perpetual Training Initiative puzzles.
  - Improved advanced video settings descriptions.
  - Made the game Hi-DPI aware.
  - Smarter default video settings.
  - Improved resolution of player avatars throughout the game.
  - Players can now be invited to play co-op on controller.
  - Button text contrast and padding has been improved when using a controller.
  - Implemented a 360° Spin action.
  - The portalgun is now correctly affected by dynamic lights (projected textures) in the scene.
  - Improved client-side prediction for coop play.
  - Added the ability for workshop levels to pack particles into their map with a particles/map_manifest.txt
  - Misc. rendering optimizations.
  - Added an icon to the game on Linux.
  - Removed the "Trading Coming Soon" button.
Bug Fixes:
  - Fixed a crash on startup that could happen on Linux.
  - Fixed a crash that could occur in some community test chambers using BEEMod on Linux.
  - Fixed the credits being corrupted on Linux.
  - Fixed the intro videos for acts 2 and 3 not playing on Linux.
  - Fixed the game starting in the top left corner of the screen on Linux.
  - Fixed a crash in the PeTI if you placed a light strip above a laser catcher on the floor and linked it to a fizzler.
  - Fixed the fizzler not playing the retract animation when turned off in new PeTI maps.
  - Fixed being able to copy 'uncopyable' items in the PeTI leading to invalid/broken levels.
  - Fixed some items in PeTI not maintaining their portalability state when expanding the chamber boundaries.
  - Fixed a crash if PeTI avatars could not be retrieved.
  - Fixed Cave Johnson's lines not progressing when playing queued workshop levels.
  - Fixed a memory leak that could occur when changing levels.
  - Fixed a bug where you could no longer ping/taunt via mouse/keyboard if you have ever used a controller.
  - Fixed the ping menu being visible when quick pinging on controller.
  - Fixed the game instructor not respecting input types for respective players in split-screen mode.
  - Fixed rumble not being respected for respective players in split-screen mode.
  - Fixed the wrong avatar being used if playing coop after playing a workshop level.
  - Fixed the OnFiredPortal2 output not firing.
  - Fixed some text being duplicated on the screen multiple times.