Inspiration
What it does
How we built it
Challenges we ran into
Accomplishments that we're proud of
What we learned
What's next for Line: draw what happens next
Inspiration
Daily Reddit games thrive on a simple repeatable loop. We wanted players to guess the future of real-world data without knowing what the data is, so we turned a hidden Wikipedia pageview chart into a daily "draw what happens next" challenge.
What it does
Each day the game shows 60 days of a mystery real-world chart (currently Wikipedia pageviews of a hidden article). Players draw their prediction for the next 21 days with a finger, then lock it in. The true continuation then draws itself next to the average line of everyone who played. The player gets a 0-100 score, a percentile, a streak and the reveal of what the chart actually was. A new puzzle is posted automatically at 00:05 UTC every day.
How we built it
tools/build_puzzles.pycompiles public-domain Wikimedia pageview data (CC0) intosrc/server/data/puzzles.ts.- Only the past 60 days are sent to the client; the correct future values stay on the server.
src/server/core/game.tsruns the daily puzzle, enforces one guess per player with RedishSetNX, and tracks scores, the crowd line and streaks.src/shared/score.tsscores by dividing error by the range of the series, giving a consistent 0-100 scale (a lazy flat line scores a median of about 45).- A scheduler posts a new Line each day at 00:05 UTC; moderators can also post it manually.
Challenges we ran into
- Keeping the future values on the server until a guess is submitted.
- Guaranteeing a single guess per player per day with an atomic Redis operation.
- Designing a scoring formula that works equally well for very different data sets, such as pageviews and prices.
What's next
- Add more public-domain data sources for a wider variety of mystery charts.
- Expand the puzzle bank with more historical series.
New and existing
This project was created entirely during the Submission Period (started 12 November 2026, after the hackathon opened on 11 November), built from scratch on Devvit Web.
