The Daily Coder ☕

A static "crossword for programmers" — one small, hand-solvable coding puzzle every morning. The pitch: AI writes most of our code now, but solving little problems by hand keeps your problem-solving sharp, the way a crossword keeps a writer's mind limber.

• Sticky hook: email newsletter ("get tomorrow's puzzle with your coffee") + a zero-login streak counter (localStorage).
• Cross-promotion: Sego Solutions footer placement.
• Site: static, hosted on My Stack. Solver state lives in the browser.
• Newsletter: a small Cloudflare Worker (worker/) on api.dailycoder.io handles signup, double opt-in, and the 7am broadcast. Subscribers live in Notion; Resend delivers.

Files

index.html            # the page (multi-file source)
assets/styles.css     # cozy newspaper theme
assets/challenges.js  # THE DATA — the only file the morning agent edits
assets/app.js         # rendering, streaks, reveal gating, archive modal, signup
assets/img/hero.png   # hero illustration (Higgs-generated)
build.js              # → dist/index.html + today.json + puzzles.json
agent/daily-puzzle.md # the morning routine's instructions
worker/               # the newsletter backend (see worker/README.md)
dist/                 # build output, what gets published

Local preview

node build.js                 # regenerate dist/index.html
python3 -m http.server 8000   # then open http://localhost:8000

(Open index.html directly too — it works from file:// since the hero is a CDN URL in the built version.)

Publishing to My Stack

node build.js
# then ask Claude to publish, or run the push command it gives you:
#   npx -y -p @mystack.co/mcp mystack-push --dir ./dist --project dailycoder ...

Reusing the same project name updates the site in place.

The daily loop

Two independent halves, on purpose — content is written by an agent, delivery is deterministic. If the agent has an off day, nobody gets a stale repeat.

6:15am ET · content — a scheduled Claude routine following agent/daily-puzzle.md:

1. Prepends one challenge object to assets/challenges.js (newest first). index[0] becomes "Today"; everything else falls into the archive. No other file changes — it's an append-only edit, about the safest automation there is.
2. Runs node build.js, which refuses to build if the ordering is wrong.
3. Publishes dist/ to My Stack under project dailycoder.

7:00am ET · delivery — the Worker's cron fetches dailycoder.io/today.json, and mails it to the Resend segment. If that file isn't dated today, it sends nothing.

Wire the content half with /schedule; the delivery half is already a cron trigger in worker/wrangler.jsonc.

Still open

• Puzzle-specific OG images — link previews use the hero illustration for every puzzle. A per-puzzle card would share better.
• Archive paging — every puzzle ships inside index.html. Fine for a year or so of dailies, then it wants splitting.
• MAILING_ADDRESS in worker/wrangler.jsonc is still a placeholder and must be a real postal address before the first send (CAN-SPAM).