Community · Monthly

Challenges

Timed problems with sealed solutions, published answers and a written review of the approaches that worked.

Cadence
Monthly
Format
Timed, sealed
Audience
All members
Moderation
Panel reviewed

Overview

A challenge is published on the first Monday of each month with a fixed problem statement, a test harness and a submission deadline. Solutions stay sealed until the round closes so nobody is anchored by the first answer posted.

When the round closes, every submission becomes visible and a panel publishes a written review of the distinct approaches — including the ones that failed for interesting reasons.

Facilities

Reference harness

Each challenge ships with a runnable test harness so correctness is objective and everyone measures the same thing.

Sealed submissions

Entries are hidden until the deadline, which keeps the round about your reasoning rather than about reading someone else's.

Published review

A written breakdown of approaches: what each optimised for, where it broke, and what the trade-off cost.

Difficulty tiers

Every round has a core problem and an extension, so beginners finish something and advanced members still have somewhere to go.

How it works

  1. 01

    Round opens

    Problem, harness and constraints published on the first Monday.

  2. 02

    Work the problem

    Any language, any approach, as long as the harness passes.

  3. 03

    Submit sealed

    Entries lock at the deadline and become visible together.

  4. 04

    Review published

    A written comparison of approaches closes the round.

Live threads

A snapshot of what the space is working through right now.

Request access
  • Round 14 — Rate limiter under clock skewSystems · 86 entries · Reviewed
  • Round 15 — Incremental markdown compilerComputer Science · 64 entries · Reviewed
  • Round 16 — Retrieval evaluation harnessAI & ML · 71 entries · Open
  • Round 17 — Log parser with backpressureData · Opens Monday · Scheduled

House rules

  • 01Submit your own work; cite anything you adapted.
  • 02Do not publish a solution before the round closes.
  • 03Optimise for readable reasoning as well as a passing harness.

Questions

Questions, answered

01How do I take part?

Build something, share the reasoning, and review someone else's work with the same care you want on yours.

02Is there a cost?

No. Participation is open; what it asks for is effort and good faith rather than a fee.

03How is feedback given?

Against the review criteria: specific, technical and about the work — never about the person.

04What is not tolerated?

Harassment, plagiarism and low-effort self-promotion. Those end participation.