Contack is a dominoes-like game for one to seven players which was patented by Parker Brothers and published in 1939.
It uses 36 equilateral triangle tiles; each side is assigned a different color and numerical value.
Play starts with the player holding the lowest-valued tile, computed by summing the three printed values for each side.
That player places the lowest-valued tile on the table as the opening move of the hand.
Scoring follows the same rules, including the matches that sum to a multiple of 5 on up to three edges.
This is followed by a repetitive draw-and-discard sequence: Another tile is drawn from the face-down pile.
If this tile cannot be played legally (matching color and either matching values or values sum to a multiple of five), it is placed, face-up, in a discard pile, and another tile is drawn from the face-down pile.
Opportunity Plays (matching two or three edges) are allowed and follow the same rules as the multiplayer version.