Okay, the Jam is on a role. 'Rotation' is the theme and that makes things...interesting.

Step one: Brainstorm about what will be the core concept of the game around 'rotation'.

After reading several of the comments, many more ideas sprang to mind. My first sticking idea was: The player walks in a 3D world, but is blocked on all sides. When rotating in a certain degree, he will notice a blocked object becomes transparent or disappears. The player will have to remain the exact rotation to go through the exit (this partially is based on Terry Pratchett's book Pyramids). This is a good option, but when I started building a small world, a better idea came to mind from the simple mechanics I created:

All I did was create a block with 4 sub blocks,  that would rotate 90 degrees on the Y axis on mousedown.

It worked like a charm, except that rotating in EulerAngles causes it to go: 0, 90, 180, -90.....which is a bit cumbersome, but for now I created a small workaround.

The core concept will be: rotating blocks, within a rotating world of rings.