From the Super Mario Wiki
Boo-ring Course is the fortieth course in the Story Mode of Super Mario Maker 2. It is set in the underground theme and in the Super Mario Bros. 3 style. It is posted by Legendary Explorer, and has a difficulty rating of 3/4 stars.
The level begins with Boo Buddies moving on a track, along with a Goomba and a ? Block containing a Super Mushroom. Eventually, Mario will reach rows of vines and the Boo Buddies will move away. After passing a Bill Blaster, Mario will reach two more groups of Boo Buddies and the Checkpoint Flag. Afterwards, Mario must cross platforms where various different types of Boo Buddies parachute in, in which he will reach the goal not long after.
"I tried to re-create a star that I visited a long time ago. It was a large, spacious place that only had Boos on it. Do you think you can get through it and return home alive?"
Names in other languages