Caution: Sink the model so the first layer is not empty!

The moving sofa problem asks for the largest sofa that can pass a hallway with a right angle turn.

In 1968, Hammersley proposed this shape defined by segments and arcs with area 2.2074...,
while the conjectured optimal area is 2.2195....

Inspired by the 15-puzzle, I turn Hammersley's sofa into a gidget/keychain.

If you are interested in creating something similar, check out prompt.txt.

Caution: Sink the model so the first layer is not empty!