TriBrix is the flat predecessor of TriAx.
A TriBrix piece consists of three disquares (1*2), with orientations that are not all the same. The criterion neatly eliminates the cumbersome 1*6 piece, and prevents a second way to form the 2*3 piece.
Here the disquares have rounded corners. The set of 18 pieces consists of all different ways a piece can be formed this way.
TriBrix © MindSports.