So you probably know how to play a platformer unless you've never played one before. Use arrow keys or wasd keys to move. Press the down arrow to get in the opening. There are tricks as well. Such as invisible grounds and false lava. Every level is indeed, possible. If too hard press the skip arrow. There is also a music button. If you press on it you should have two buttons, classical and energetic. Press the R button to reset the music button.
