Does not look like it from render but this is a D6. You read the numbers on the points of the 8 sided diamond in the center of the cube. The number you roll is obvious from dead on but not so much on an angle.
Plays similar to crazy 8s except there is no wild at begining of game. When a player can not play they pick up a card like normal. If they still can't play they roll the die and that card is wild until the die is rolled again.
this large 85mm diameter spherical D15 is for the true Math geek. Numbered with all 15 primes of Monstrous M theory it is sure to get people talking. Even though the landing surfaces are all flat there is a large spherical weight which will help the die always land on a valid side.