If your game screen is flickering or flashing on your Mac, it is likely because the game’s older display technology is struggling to keep up with your high-speed monitor. Please try these steps in order:
Lower the Refresh Rate (ProMotion)
Many newer Macs (MacBook Pro and iMac) use 'ProMotion' technology, which allows the screen to refresh up to 120Hz. Older games often cannot handle this speed and will flicker.
Open the Apple Menu and select System Settings (or System Preferences).
Click on Displays.
Locate the Refresh Rate dropdown menu.
Change the setting from 'ProMotion' to 60 Hertz.
Restart your game to see if the flickering has stopped.
Toggle Full-Screen Mode
Sometimes the Mac 'Spaces' feature conflicts with a game's full-screen rendering.
While the game is open and flickering, press Command (⌘) + F.
This will switch the game to Windowed Mode.
If the flickering stops in a window, you can try resizing the window or checking the game's internal Options menu to see if you can lower the resolution before switching back to Full-Screen.
Open in 'Low Resolution' Mode
If you have a Retina display, the extremely high pixel count can overwhelm older game engines.
Close the game and open your Applications folder.
Find the game icon, Right-click (or Control-click) it, and select Get Info.
Look for a checkbox that says Open in Low Resolution.
Check that box, close the window, and launch the game again.
Note: If you do not see this option, it means the game or your macOS version does not support this specific toggle.
Disable 'True Tone' and 'Night Shift'
In rare cases, the Mac's automatic color adjustment features can cause a 'strobe' effect or flickering in older software.
Go to System Settings > Displays.
Toggle True Tone to Off.
Click the Night Shift button and ensure it is set to Off.