Still a Triangle!

Nutmeg and Clover have a puzzle piece on their low table. It is a flat yellow shape, resting quietly in front of them. Together, they count its straight borders. One, two, three sides meet at one, two, three pointy corners. It is a triangle. Watch the piece gently turn sideways in our clear diagram. The flat yellow shape turns around, pointing toward the side. Now it rotates further until it points straight down. Even turned completely upside-down, it keeps its three straight edges and three corners. No matter which way it turns, it never loses a side or a corner. It is still the very same triangle!