- Tertrominoes are observed (or) assumed as if they are fixed into only being in "Orthogonal" rotations.
- "Orthogonal" refers to being lined up with the horizontal and vertical axes.
- Mirror symmetry can occur only along \(2\) axes.
- Reflection along the horizontal axes is called the \(X\)-Reflection.
- Reflection along the vertical axes is called the \(Y\)-Reflection.
- Every tetromino can have \(1\) of \(4\) possible symmetries. ("Symmetric with \(Y\)" (or) "Symmetric with \(X\)" (or) "Symmetric to both" (or) "Unsymmetric").