Getting started

Pick a puzzle

Open the app and choose a puzzle from the catalog. Puzzles are grouped into five tracks — Algorithms, Database / EF, Refactoring, Architecture, and Secure Coding — and rated Easy to Hard. Every puzzle states the goal, the constraints, and the bar you’re expected to clear.

Run, then submit

There are two very different buttons, and the distinction matters:

• Run executes only the visible sample cases (plus an optional custom input you type yourself) and shows you the return value and your Console.WriteLine output immediately. Run is free-form and uncounted — iterate as much as you like.
• Submit grades you against the full hidden suite, including the large performance tests. Submissions are what count toward your daily quota on the Free plan.

A good rhythm: Run until the samples pass, think about the complexity, then Submit.

Reading your results

Each test reports pass/fail, server-measured elapsed time against its time budget, and allocated bytes. Failures show a character-level diff of expected vs. actual. Hidden tests mask their input and output — you see timing and pass/fail only, so the suite can’t be reverse-engineered.

Stuck?

Every puzzle has a reveal solution option: load a correct, optimal reference into the editor, study it, then reset and try to beat it from memory. No penalty, no shame — that’s deliberate practice, not cheating.

Your progress

Solved puzzles are marked with a ✓ and your in-progress code is preserved per puzzle, so you can close the tab mid-thought and pick up where you left off.