Heighway dragon

A plane curve generated by recursively folding or by a suitable L-system. One drawing convention uses the productions $a\mapsto aRbFR$ and $b\mapsto LFaLb$, where $F$ moves forward, $L,R$ turn by $90^{\circ }$, and $a,b$ expand but do not draw. Summaries of whole expanded blocks permit a position after a large number of forward steps to be found by descending only into the block containing that step.