This is easy but I couldn't find example file anywhere so I made one for reference.
Move character with WASD
Box Blue - Static Box will knock you back
Box Red - Moving Box will knock you back
Box Green - Will slide back
Box Yellow - Will bounce back
-Don't let the boxes hit eachother. They have no script to interact with eachother and will throw error.
-If you jump on them they may bounce/slide back forever, and take you along with them.
This kind of thing will help people get into Godot a lot I feel and it's nice to see other people have the same idea, I like you're showing multiple knockback styles too. I've got a plan myself to release a couple of projects I'm working on open source at a certain stage and they will be a turn based grand campaign style game and FPS/RPG. Show people exactly how to do specific mechanics and then people can use that as their templates for the projects they're working on to get a quick start on whatever game they like.
By the way, to solve the error it would just take throwing an if statement at it and then stopping the code.
Thanks for the tip 
