Baseline (Widescreen) Solution & Issues
Widescreen resolutions are listed in-game. Everything scales correctly.
Gameplay scenes are designed for 16:9; narrower aspect ratios have slight horizontal cropping (this does not affect gameplay).
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
There are resolution options found in the registry. They can be edited, but the game resets them back to closest supported widescreen res.
HKEY_CURRENT_USER\Software\Zojoi\Shadowgate
Eyefinity / Surround Specific Solution & Issues
4k UHD Specific Solution & Issues