The board
How the board works
Everything about the board follows from one requirement: it has to be safe to leave face-up on a table.
The board
The board and the legend
Your patient’s screen is a grid of colored buttons. No words, no labels, no headings. The list of what each one means is written once, encrypted, and shown only after a PIN — on their phone as well as yours.
So the board itself opens instantly, with nothing to unlock, which matters twice over. A tracker you have to log into doesn’t get opened in the middle of an exposure. And a tracker that shows a colored dot and a 72 to anyone who looks is one your patient can use on a bus, in a waiting room, or across a kitchen table from someone who doesn’t know they’re in treatment.
Encoding
Telling the six buttons apart
Six colors and one shape, or six shapes and one color, or six of each. Any of those works. What doesn’t work is six buttons drawn from four colors, where two are near enough the same green that your patient falls back on grid position to remember which was which — at the exact moment they are least able to.
Colored circles are the default because they are the version someone actually wants to open. The other two are there for people who need them: roughly one in twelve men has some degree of red-green color vision deficiency (Birch, 2012), and to them a board encoded in hue alone is six identical circles. Your patient picks; the meanings stay the same either way.
The colorblind-safe palette is fitted against simulated protanopia, deuteranopia and tritanopia, so every pair stays distinguishable under all three at once. Six is the number of colors that still allows for that.