Checklist

The kit’s check keys in nested groups. A group’s key is the sum of its items: all done, none, or some, and some is a key sunk halfway with a bar across it. The head counts the items, “3 of 7”, and its lamp lights when they are all done.

Press a group: everything under it follows. Press an item and the groups above it change. Arrow keys move; Space presses.

• Every item is a real checkbox in a label, so it is named, toggled by Space and posted by a form without any of this being reinvented.
• A group with some items done is indeterminate, which the browser reports as mixed, and it carries aria-checked="mixed" as well; a screen reader says “mixed” where a sighted reader sees the half-sunk key.
• The half-sunk key has a bar printed on it, so it reads without colour or depth in either finish. A finished item is struck through in ink, not faded.
• The list is one Tab stop with the arrow keys inside it, so a long checklist is one press of Tab to pass; right and left arrows step into and out of a group.
• The count, “3 of 7”, is a polite live region; the lamp beside it is only a second signal for “all done”.
• Pressing a group that is already all done clears it. Pressing one with some done ticks them all: the same as any checkbox that is not ticked.