Guide to the Godot game engine/Platform specific

When gaming was young, games were rarely designed for multiple systems at once. When that started, people had to check every screen resolution worked. When phones started coming in many different shapes and sizes, this soon became impractical, and even impossible for most of us. Godot has a way to combat this, of course. But screen size is not your only problem.

Stretching the screen
Go to ProjectSettings, and find Display -> Window. Go to the bottom of the area on the right, and under "Stretch", there are 3 settings: Mode, Aspect and Shrink.

As the  value gets bigger, the screen resolution goes down.