ref: 9ce0a6d93212ffc0986a2b399fd8e9e983f62904
parent: 05c536e50d0c3114e1de5283eac97ff22bad0fc7
author: Simon Tatham <anakin@pobox.com>
date: Sun Feb 5 07:05:28 EST 2023
Pearl: fix bounds check in previous commit. Ahem. That's what I get for testing the fix on a square puzzle.