Physics Layers

By default, The Platformer Game Kit uses several of Unity's inbuilt physics layers and uses the SetupDemoLayers script to automatically configure their Collision Masks in Play Mode so that it doesn't need to modify your project settings in case you want to import it into an existing project. But for a real project it is better to use custom layers with meaningful names so the SetupDemoLayers Inspector shows a button to Create Custom Layers.