What should I do when the three hats start disappearing?

Keep moving right and use short jumps through the hat line; the hats clear in stages and lead into the monster-crowd phase.

When is it safe to go to the door?

Wait for the floor crowd to clear, collect the yellow key, and confirm that the chained door is now a dark open doorway before entering.

Mr Potato level guide

hard

Clear the three question-mark hats and the later monster crowd, collect the yellow key, and enter the opened door on the right.

Layout: The potato starts on the far-left floor. Three question-mark hats occupy the middle of the room, small round monsters appear beneath them, a yellow key lies below the central section, and a chained door stands on the far right.
Goal: Finish the hat and monster sequence, take the yellow key, and enter the right-hand door after it opens.
Opening: Move right into the hat line and use short jumps to disturb the hidden occupants across all three hat positions.
Danger Zone: After the hats reduce, identical monsters spread across the floor. Keep moving and jump clear of the crowd instead of walking directly into it.
Mechanics: The hats hide a staged monster sequence; after the floor crowd clears, one floating monster with a red heart remains and the right door changes to an open dark doorway.

Keep advancing across the three hats so the sequence continues instead of waiting at the left edge.
Use the cleared floor to collect the yellow key, then treat the opened dark doorway on the right as the final state check.
Think in chain clears. The best move is the one that sets up the next two moves, not just the quickest current match.

Start on the far left and walk right to the first question-mark hat.
Jump through the hat line, continuing across all three positions as the hats and hidden occupants disappear in stages.
When the small monsters spread across the floor, leave space and use jumps while the crowd clears.
Take the yellow key from the central floor after the crowd is gone, watching for the remaining floating monster with the red heart.
Continue right and enter the dark open doorway when the chained door has opened to trigger victory.

Stopping after the first hat disappears leaves the staged sequence unfinished.
Walking straight through the floor-wide monster crowd can knock the potato back before the room clears.
Entering the right side before taking the key and confirming the door has opened skips the actual exit state.

What should I do when the three hats start disappearing?
Keep moving right and use short jumps through the hat line; the hats clear in stages and lead into the monster-crowd phase.
When is it safe to go to the door?
Wait for the floor crowd to clear, collect the yellow key, and confirm that the chained door is now a dark open doorway before entering.