Tip: Switch palace switches normally disappear if you replay the level. However, if you insert them as direct Map16 and use the hex-edit at $00EEB2 in the ROM map, you can replay the level without a problem.
This block acts differently for Mario when he is on Yoshi and when he is not. I thought it might be useful as a contraption or level gimmick. Can also be used to de-cheese levels, like by preventing bringing a Yoshi back through a pipe. Includes a function that removes Yoshi if Yoshi is inside the block. By default it acts as a cement block when riding Yoshi, and an air block when not.
This version optimises the code and adds SA-1 support.
Tested with: LM 3.11, GPS 1.4.1, SA-1 1.32, Snes9x 1.60. Works as intended, and now it's optimized, so accepted! (Added gif during moderation)
I'm still unsure about the "Kill Yoshi" function, but at least it can be turned off so it's not a big deal.