Manage your Codeforces Polygon problems from a desktop app — no web UI.

Decagon lets you edit problem statements, tests, solutions, files and scoring, build packages, and commit revisions — all backed by local folders you control. Each problem is one folder bound to one Polygon problem.

Independent project, not affiliated with Codeforces. Pushing the final package into a round still happens on the Codeforces website.

Screenshots

Info — limits, checker/validator, points mode	Statements — per-language fields & resources
Files — solutions, source, resources & attachments	Tests — groups, points & generation scripts

Get started

1. Install — download the installer from the Releases page, or run from source: npm install then npm run dev.
2. Add your API key — in Polygon, go to Settings → API keys and create one. Enter the key and secret in Decagon (stored encrypted on your device; it never leaves your machine).
3. Create or import a problem:
   • New project — scaffolds a local folder. Open it and either bind an existing Polygon problem id, or create a brand-new problem on Polygon (with any name).
   • Import from Polygon — pulls an existing problem by its id into a new folder.

How saving works

This is the core idea, so it's worth 20 seconds:

• Save writes to your local folder only. Each file and section has its own Save button, enabled only when you have unsaved changes. (In the Tests tab a single Save tests button writes that testset's tests, scoring groups and generation script together — still local only.)
• Push to Polygon uploads your saved folder to Polygon. Nothing reaches Polygon until you push; unsaved edits aren't pushed, and Decagon warns you. A progress bar shows what's uploading, and re-pushing is incremental — only the tests that actually changed are re-uploaded.
• Pull downloads the current state from Polygon into the folder. Files you keep locally that don't exist on Polygon are preserved (not deleted).
• The folder is watched: if it changes on disk, Decagon reloads automatically. If a file you're editing changed outside the app, it asks whether to keep your in-app version or load the version from disk.

What each tab does

Tab	What you do there
Info	Time/memory limits, input/output files, interactive flag, checker/validator/interactor, and points mode (off / on / treat checker points as %). Clearing a checker or validator and pushing unsets it on Polygon.
Statements	Edit each field (legend, input, output, scoring, notes, …) per language, plus shared resources (images, .sty).
Files	One place for every file, in four sections: Solution files (each with a tag — main, correct, wrong answer, TLE, …), Source files (generators, validators, checkers — use testlib.h), Resource files (headers, .sty), and Attachments. A unit's Type dropdown moves it between sections, and a per-file checkbox controls whether it's pushed. Resource files support experimental grader advanced properties (stages / assets / cpp.* python.*).
Tests	Manual and script-generated tests per testset, scoring groups (points/feedback policy, dependencies), and points per test. The generation script and the test list stay in sync: editing the script updates which tests exist, and drag-and-drop reordering of tests rewrites the script to match. Bulk-edit groups/points across many tests.
Validator tests	Feed an input to the validator and assert it's accepted or rejected.
Checker tests	Feed input/output/answer and assert the checker's verdict.
Packages	Build a package (full / verify), see its status, and download the ZIP.
Commit	Save a revision of your working copy on Polygon.
Manage access	View your access level (read-only — change collaborators on the Polygon site).

A sidebar on the right stays visible across tabs: a Project status card summarizes the problem at a glance (statements, checker/validator, test & solution counts, owner, access, revision, latest package, uncommitted changes) and a Notifications panel keeps a log of recent actions so toasts that auto-dismissed aren't lost.

Writing generation scripts

Decagon uses Polygon's script format. Each line runs a generator and writes one or more tests:

gen 1 5 > 3        # write a test at index 3
gen 1 5 > $        # write to the next free index
gen2 4 7 > {1-3,7} # one run that produces several tests (indices 1,2,3,7)

Edit the script and the test list updates; reorder tests by their drag handle and the script's target indices update to match. Generators are produced by Polygon on build, so generated tests show their command as a placeholder until you build a package.

A typical session

1. Pull (or Import) to get the latest problem state.
2. Edit a statement / solution / test, and Save that item.
3. Push to Polygon when you're happy with the saved changes.
4. Build a package in the Packages tab and download it.
5. Commit to save a revision.
6. Upload the package into your round on the Codeforces website (manual step).

Good to know

• Removing a test locally and pushing deletes it on Polygon. Other items (files, solutions, statements, resources) have no delete API — remove those on the Polygon website. Validator/checker tests can only be added or edited here, not deleted.
• Local-only files kept in your folder but not on Polygon survive a Pull.
• Testsets can't be created here (no API) — make them on the Polygon site, then Pull.
• Binary files (e.g. statement images) are pulled but not pushed back.
• Stress testing and access management have no API, so they aren't editable here.

Built with

Electron · React · TypeScript · electron-vite.

License

MIT