I was looking through the games assemblies with ILSpy for modding purposes and found some references to devtools

1. Right-click Sulfur in Steam, and go to the launch options.
2. Add: -dev true
3. Start game.

Use F1 to shows stats, use F2 to hide HUD and F3 to open the DevTools.

You can spawn guns, teleport to any level and do much more! Have fun!