Upside-down tetrahedron fitted in a hole. Side facing up changes every so often, randomly.
Every 16,441883670018201742414 Earth days, a value from 0 to 0,62 is chosen.
16 days, 10 hours, 36 minutes, 18,749089572632158252 seconds.
0 = nothing happens
1-15 = side number 1
16-30 = side number 2
31-45 = side number 3
46-60 = side number 4
61 = divide by 2, round to lowest
62 = multiply by 4 and divide by 6, round to lowest