Dealing with the "Fatal Error: Cannot set display mode" Serious Sam 3: BFE usually means

The “Cannot set display mode” error in Serious Sam 3 stems from an outdated display mode enumeration method. It is but a software compatibility issue. The most reliable fix is to manually force the resolution and full‑screen state via launch options or editing GameSettings.ini . Disabling full‑screen optimizations and temporarily lowering the refresh rate to 60Hz resolve the majority of remaining cases.