Sorry for the forum spam ;)
Here's another thing you might try: forcing the game to run on the NVIDIA GPU; Game Maker games like Nuclear Throne seem to have similar issues.
1. Open NVIDIA Control Panel.
2. Go to Manage 3d Settings, then select the Program Settings tab.
3. Use the Add button to browse to Cthon's exe file and select it.
4. Click the Apply button and then run the game.