THIS IS HARD A quick lesson (VERY IMPORTANT) not sarcastic (read all to understand mechanics) » You might think the player is scrolling but that would make the player go off-screen. So we can infer that the stage is actually scrolling even though the the code might be in the character, to prove it look inside the level sprite and see the x and y axis changing! It is VERY IMPORTANT to understand the mechanics of the game if you were to create your own scrolling platformer.
Might update if popular! If you use the code then PUT CREDITS or I will report