What Counts as Supat
The word has a border, and the border is where the whole debate lives.
The rule: supat is the gap between the bed and the floor - specifically the under-bed void where you can see the floor through. That is the canonical slot. "The cat hid in the supat" means the cat is in that under-bed space.
The borderline cases: is the space under the sofa supat? Is the gap behind the door? Is the seam between the mattress and the headboard? The word was never going to settle the border, and the border is exactly what people are arguing about. The trend lives in the "is that a supat?" question, not the answer.
How the detector plays it: a room with several gaps. One is the true under-bed supat, the others are decoys - under the sofa, the doorway, the seam. You call which is the real one in three seconds. Miss and the card shows you the border you drew wrong.