Arrow Keys to move. This is a game engine, you can use this in your project. This engine has vertical levels, next and back levels. You can use this by giving credit to me.
Thanks to @ProgrammerLightYears for the main physics of the player. I was using my own but I had a problem. The problem was that- when the player went to the top of a wall or a ceiling when he touches those. Thanks to @griffpatch for some idea! If you are unable to use this in your game for some reason then please inform me!