Dominoes 03-01 (reversed) pairs, and generic backsides. Dominoes Dominoes is a family of tile-based games played with rectangular "domino" tiles. Each domino is a rectangular tile with a line dividing its face into two square "ends". Each end is marked with a number of spots (also called "pips", "nips", or "dobs") or is blank. The backs of the dominoes in a set are indistinguishable, either blank or having some common design. The domino gaming pieces make up a domino set, sometimes called a "deck" or "pack". The traditional Sino-European domino set consists of 28 dominoes, featuring all combinations of spot counts
Schläfli double six double six configurations. The set of 15 lines complementary to a double six, together with the 15 tangent planes through triples of these lines, has the incidence pattern of another configuration, the Cremona–Richmond configuration. The intersection graph of the twelve lines of the double six configuration is a twelve-vertex crown graph, a bipartite graph in which each vertex is adjacent to five out of the six vertices of the opposite color. The Levi graph of the double six may be obtained by replacing each edge of the crown graph by a two-edge path. The intersection graph of the entire set