I recently purchased Game Maker professional since I am going to work with my sister to finish her game. I've been playing around with the engine along with the Box 2D physics engine and its pretty cool. I finally found out the trick with tile set collision detection. It seems that they do it just like Sonic 2's platforming. Where you have a tile set just for display and a mask for collision. I'm used to other engines where the tiles have unique properties. I also got the vertical moving platform working good but horizontal is being a pain since my platform does not have a speed due to it moving along a path. I might end up making an IWBTG clone as a side project.