We now have a first fully working version of the game. It can be played here. It is possible to win, though randomised shuffling means it is not always possible.
You may notice that I have trimmed the borders of the cards. I cheated and did it in Affinity Photo by using rectangular marquees as shown at the side here. In each position of the marquee I filled with white. On a later page I still intend to describe how it could be done in JS.
There are still some improvements that could be made and they will be the subject of the remaining pages. The .js files that change will have suffix C from now on.