Colorblindness makes it hard to tell whether LEGO parts in a set are actually different colors. Enter a set name or number and it lists every part that comes in colors similar enough to confuse, for a chosen color vision deficiency, ordered most confusing first.
Each part's colors are simulated as the selected vision type would see them — Viénot 1999 for protanopia and deuteranopia, Brettel 1997 for tritanopia (ported from public-domain libDaltonLens), and a luminance projection for achromatopsia. A severity slider interpolates from normal vision to full dichromacy and regroups the parts in real time; swatches next to each part show the simulated colors. Colors whose CIEDE2000 distance falls under a threshold are grouped as confusable, with a dim-light option that lowers lightness before comparison. Transparent and solid parts are never considered confusable with each other.
The browser does all the color math and rendering with vanilla ES modules. No framework, no build step. Part figures are created once per set; moving the controls only recomputes groups and moves nodes.
A small Node server (server/server.mjs, no dependencies) serves the static files, proxies two Rebrickable API endpoints so the API key stays private (following pagination, caching responses on disk for a month), and regenerates the color table and set autocomplete list from Rebrickable's published CSV dumps on boot and daily. Everything derived lives in cache/; all writes are atomic, so the container converges to a working state from any starting point, including an empty cache.
cp .env.example .env # add a Rebrickable API key and Cloudflare tunnel token
docker compose up -d
Stock node:alpine with the repo bind-mounted read-only — no image to build. Traffic arrives through the Cloudflare tunnel; nothing is exposed on the host.
For local development:
REBRICKABLE_API_KEY=... node server/server.mjs
node --test test/
The tests verify CIEDE2000 against the Sharma reference pairs and the simulation and grouping pipeline against known confusable LEGO color pairs.