Mario is supposed to be small, and waits at the bottom until an icicle drops a vine from above. Spike traps make it so you cant climb the vine with diagonal joystick movement, and it shouldn't be possible to do a buffer jump since the vine won't come down for a while.
I'm not an expert in tech so if anyone manages to break it let me know!
Actually I've learned it's not unrealistic for people to chain buffer jumps with this setup. Maybe I can move the fishbone up so that you are forced to land on the ground with a mushroom, but that hinges on whether you can initiate a crouch while doing a buffer jump.
I could maybe make the vine longer so you'd have to chain a lot of jumps, or maybe theres a way to prevent the initial buffer jump (on-off under the door maybe?)
Looks like you can't initiate a crouch with a buffer jump, so if you move the fishbone above the hidden block, and force Super Mario out of the pipe, it should be cheese-proof. If not, maybe that's more impressive than the level itself :3