Windmill Hills and Chuck Boss broke spectacularly.
Nightwalk can be completed without pressing any buttons, can be desynced with L/R, and you can kill yourself in it by holding the jump button.
Submap in a Level is incredibly buggy when it comes to snapping Mario to the path and Mario's walking animation.
I'm not sure what Powerup Stacking is supposed to be showing. It's not the exploding key because 1-1 of the level submap showed this off much better, and the key spawned into existence and exploded on me while I was messing with the turn blocks to the left looking for powerups to stack.
A lot of this looks really promising and can be really good in the future. But I'm going to be honest with you; this was clearly not ready to be shown off.