Baseline (Widescreen) Solution & Issues
The game should initially run at your native resolution.
You can adjust resolution and refresh rate under Help & Options, Settings, Display.
Settings are stored in C:\Users\\AppData\Roaming\Doublefine\TheCave\screen.dat
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
Native support, no problem found.
Cosmetic nanoblemish: main menu's backdrop (also seen during opening/closing cut-scenes) was not designed for aspects wider than 16:9.
Eyefinity / Surround Specific Solution & Issues
If graphics look distorted even though in-game resolution setting is correct, Save & Exit then restart the game. This should fix the aspect ratio.
Initial character selection is Vert- (unnecessarily zoomed in). This is fixed as soon as your first character gets moving.
In quite a few places throughout the game, the camera loses focus and characters get stuck on a side screen, unable to move. Only solution is to switch to a single screen res and restart the game.
4k UHD Specific Solution & Issues