Mimizu
1. Mimizu is Japanese for “earthworm”.
Numbers are entered in order, as if we were numbering an earthworm from head to tail, starting with “2”. This earthworm can only pass through openings, of course.
2. Openings.
Light gray walls are "open". Adjacent hexagons with an opening must be consecutive numbers OR share a common prime factor. Conversely, consecutive hexagons or hexagons that share a common factor must have an open wall between them.
3. Walls
Solid black walls are "Closed". Adjacent hexagons with a wall cannot be consecutive AND cannot share a common prime factor … and vice-versa.
4. Instructions with pictures