Call of Cthulhu/Non-Euclidean Geometry

"Non-Euclidean geometry, literally any geometry that is not the same as Euclidean geometry. Although the term is frequently used to refer only to hyperbolic geometry, common usage includes those few geometries (hyperbolic and spherical) that differ from but are very close to Euclidean geometry."

ref: https://www.britannica.com/science/non-Euclidean-geometry