Well, sorry, but this (Newer SMB Arcade) is not being developed anymore currently, although I did release the physics engine (and finished it, including the ability to add more platforms easily, the ability to make differently-shaped walls and ceilings, and more!) in a separate topic called “Advanced Platforming Collision Engine” (which I would link to, but it hasn’t been approved yet at the time of me writing this.) I hope you like it and can use it, it’s not a huge project, so I think someone (and future me) could build a game around it.
In case this post is approved before the other topic (and so it’s easier to get to, here’s the engine!
And, to make it even easier to use, the collision and the actual object images are different (MAKE SURE FOR SPRITES THE COLLISION OBJECT WIDTH AND HEIGHT ARE THE SAME DIMENSIONS AS THE OBJECT.) Also, try to use as few pixels of collision as possible, as this will make your game perform better!