Pictured: A simulated hyperbolic geometry in which parallel lines diverge, so that the higher one goes, the more space there is. The shapes that are stacked on top of each other in this image are completely cubic and congruent.
Source: Portals to Non-Euclidean Geometries, ZenoRogue on YouTube (2022).
You've learned about regular geometry, on a three-dimensional plane of existence (our world) — things like the Pythagorean Theorem and whatnot. But what happens when the number of dimensions changes? Or when the dimensions aren't plane-shaped anymore, but spheres or saddles? These concepts have been one of physicists' fascinations since the 1800s.
This website is meant to provide a brief insight into all that non-Euclidean geometry has to offer. See the Conventional Euclidean Rules tab to look at the history of "normal" (Euclidean) geometry.