Different "modes" such as Newtonian gravity and ambient heat can be toggled in the top right hand corner, or if you click the little check at the bottom of the screen.
@deth(View Post) This is for the "simulation mode" menu. You can change various play settings there.
The rainbow button next to it is the "view mode" menu. This allows you to change how things look like. The same happens when you use the number keys 1-9 above the regular keys. (Not on the right edge of the keyboard!)
Some quick buttons are also available on the top right, they have letters on them.
@jenn4(View Post) I doubt he meant game modification, but that could be it. The hint on "How to get them" might mean that he does, but that isn't definitive.