TENKA_BACKconstant

The field's colour, in place of the back's own: #8f2826, rebeccapurple, rgb(…). Anything else is ignored.

The colour of the lines and dots on the field.

The colour of the paper round the field.

Words in the middle, such as a site's name or mark ("五つ", "一つ"), in place of the back's own ornament.

The width to draw at, in pixels; the height is 1.4 times it. Unless said, the drawing has no size and fills what holds it.

What a screen reader says for it. Unless said (or said as ""), the back is decoration and says nothing.

Your own artwork for the whole back: SVG markup drawn in the 100 by 140 box, over the paper, in place of the lattice and the ornament. It is the page's own markup: scripts, handlers and foreign objects are taken out of it.

Your own picture for the whole back, in place of the lattice and the ornament: a data:image/ address, an https: address, or an address on your own site. It fills the card inside its rounded edge. Drawn into a page it loads like any image; as an image of its own (cardBackUrl) only a data:image/ address can load, which is how browsers treat a picture inside a picture.

Your logo, in the middle of the back: SVG markup drawn in a 100 by 100 box, or a picture's address as for image. Over the lattice it sits on a plate of the paper's colour; over your own art or image it sits as it is.

How wide the logo is drawn, in units of the 100 wide card. Unless said, 34; at most 80.