Godot is a great sketchpad for these things. One time I was at the airport for a flight, so I wrote a quick-and-dirty notepad for the Russian pencil-and-paper game Virus War (“Война вирусов”) for my eInk tablet that my partner and I could play. It was just a grid with tappable buttons in varying states, but I was able to get a playable prototype ready for our flight.