This two piece puzzle has fourteen (I think) ways of going together – only one is right. Show your friends the dodecahedron, then time them assembling it correctly.
It is basically a complicated nut and bolt.
The file SwirlCore.stl has the 'bolt' thread with height 120mm, and thread diameter of 50mm.
The file SwirlDie.stl is a slightly enlarged 'bolt' with a thread clearance of 1.5mm – we use this to cut the thread in the 'nut'
I chose a Dodecahedron for the toy shape.
The very clever mathematician who came up with the points had no idea how it might be used! I had to work out how to rotate and shift the points to give a dodecahedron sitting nicely on one of its faces.
We use 'difference' in Openscad to subtract SwirlDie from the toy shape to get the outer 'nut'
To get the shaped bolt to fit that nut, we first have to make another die; this die is made by subtracting the toy shape from a big block ot cylinder.
Now we subtract this new die from SwirlCore to get the inner shaped bolt.

You can, of course, make up your own shape.
Edit the Openscad file for your shape instead of the dodecahedron – make sure to edit the 'import' statements to point to the directory you have stored SwirlCore and SwirlDie.
You should be able to use 'scale({X,X,Z])' in front of the 'import' to adjust the bolt height to Z120mm and diameter to X50mm.

I was able to print the inner part without a brim, but the outer had to have a substantial brim to get it to stick!