@Enbybookwyrm Some of this is a matter of definitions. Strictly, an #icosahedron, or any #polyhedron, is a 3 dimensional figure and a "4-d icosahedron" is an oxymoron, like a "3-d square".

There are 4- and n-d analogs of polyhedra, called #polytopes. Instead of polygons meeting at vertices and enclosing a volume of 3-space, you have (in 4-d) polyhedra meeting at vertices and enclosing a volume of 4-space. You can argue one of these is analogous to an icosahedron, but only analogous.

Discovered a great channel on YT about #geometry, #polytopes, etc

Here's a nice example:
https://youtu.be/KnJRtxJ5taM