Steam AutoCloud has been enabled for Windows. It is untested on Steam Deck at the moment, but should work assuming Proton Compatibility mode just simulates the Windows file path. I don't own a Steam Deck so if anyone can confirm that, that'd be cool.
PATCH NOTES
v1.0.11
Save files can be transferred between devices now
made some of the swings wider
icicle hp 3 -> 4
escape sequence missile part is easier now
escape sequence fan section has elec plugs now
added more easy mode platforms
hard mode has banana peels now
various level adjustments
v1.0.12 - v1.0.14 (Beta branch only)
Hotfixed & tested a lot of save backup issues (Thanks to SeymourSchlong)
v1.0.15
lowercased the "a" in "are" in all references to the title, including the executable
fixed a bug where the ending result time could be 10-30 seconds longer, despite save file time
Re-recorded the tutorial again
various level design tweaks