The thing under his foot was very small, about the size of a pinky nail, and slightly sharp. It seemed to be stuck to the ground, which was why Deathstroke had felt it digging into his sole when he kicked it just now.
He bent down and felt around with his hand. Humans still relied more on their upper limbs for sensory input. Feet could work too, but people were more accustomed to using their hands to determine an object's shape.
It was like waking up in a pitch-black room and searching for the door. Even though legs were longer than arms, people usually stretched out both hands to slowly feel their way around instead of using their feet.
"Feels very hard. Hmm, and somewhat flexible. Solid. It has three wedge-shaped faces, but from another angle, it seems to have a triangular opening."
Smiling thanks to his good luck, Deathstroke groped at the invisible object on the floor while describing its shape to himself.
"Eek."
There was no need for a verbal description. Strangle, who could share the sensation, let out a cry. It reminded its host that this structure had a corresponding name in his memories: the Penrose Triangle.
Its essence was that faces located on different planes, when viewed from a particular angle, formed a triangle on a two-dimensional plane. It made people think it was a three-dimensional object, but it could not exist at all in the Third-Dimensional World. It was a projection of four-dimensional space.
That long explanation was abstract. Anything related to mathematical geometry was like that, yet concepts of space happened to be closely tied to such things.
Still, it could be explained in one simple sentence—the Penrose Triangle was something that could not exist in reality.
"Yeah, it's a Penrose Triangle. And it