It looks a little like a fedora, and it's what's known as an "Einstein tile." Meaning, unlike other shapes, if it's laid out and slotted together over and over again, it doesn't easily repeat itself.

The recently discovered “hat” aperiodic monotile admits tilings of the plane, but none that are periodic [SMKGS23]. This polygon settles the question of whether a single shape—a closed topological ...

What just happened? A group of mathematicians created a "new" polygon previously known to exist only in theory. It's a 13-sided shape that they dubbed "the hat," even though it only vaguely resembles ...