§ A walkway of lanterns (WIP)

§ Semidirect products

[10aX][10bY]=[10a+XbXY] \begin{aligned} \begin{bmatrix} 1 & 0 \\ a & X \end{bmatrix} \begin{bmatrix} 1 & 0 \\ b & Y \end{bmatrix} = \begin{bmatrix} 1 & 0 \\ a + X \cdot b & XY \end{bmatrix} \end{aligned}

§ A walkway of lanterns