# Diagonally directed

For a diagonal direction $d$ (e.g., up and right), we say a polyomino is "$d$-directed" if every cell of the polyomino can be reached from an anchor cell by going only in one of the orthogonal components of $d$.

For example, the following polyomino is up-right-directed with the bottom-left cell as an anchor, since every cell in it can be reached from that cell by going up and right, and not down or left:

Unlike orthogonal directedness, the anchor cell for for a diagonally directed polyomino is uniquely one of the corner cells of the polyomino. Furthermore, a diagonally directed polyomino must be orthogonally directed in each of the orthogonal components of its direction (e.g. the polyomino above is both up-directed and right-directed).

In most other sources, "diagonally directed" is usually just called "directed".