From the Super Mario Wiki
Impassable Castle is the forty-sixth course in the Story Mode of Super Mario Maker 2. It is set in the castle theme and in the Super Mario Bros. 3 style. It is posted by Father of Name Withheld, and has a difficulty rating of 3/4 stars.
The level begins with some Thwomps that Mario must avoid, with one of them defeating a Big Chain Chomp. Mario must then equip a Buzzy Shell and use it on another Thwomp so that it properly hits a Big Chain Chomp. Mario must then correctly align a Thwomp so that it destroys a series of Brick Blocks to clear a path forward, then avoid a few more Thwomps to the Checkpoint Flag. After having more Thwomps defeat Big Chain Chomps, Mario must then have a Big Chain Chomp in a Koopa Clown Car be defeated by two Big Thwomps in order to reach the ax at the end.
"GWA HA HA! This castle is protected by Thwomps and Chain Chomps! There's no way Mario is getting through! Well, unless he figures out that he can pick up Buzzy Shells with and tilt ↓ to wear them as helmets! BUT THAT AIN'T GONNA HAPPEN!"
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