Horizontal mouse movement can now be inverted, this can be toggled in the settings menu.
Let me know if you find any game-breaking bugs.
Horizontal Mouse Inversion.
Source: Steam Community (opens in a new tab)
Build and release context
Steam update times within 24 hours of this post. Matching dates do not confirm which build it describes.
Build 13695331 · public branch
Steam updated · First observed
Build 13689424 · previous branch
Steam updated · First observed
Build 13695331 · beta branch
Steam updated · First observed