# Penumbra Chess

> Penumbra Chess is offline chess training software for Windows and Linux by Harmecs Labs (Altendorf, Switzerland), with an Android app coming soon to the Play Store. A local Stockfish 19 engine acts as a coach: it shows up to three coloured move suggestions but never moves by itself. Includes an opening book with 3,919 lines covering all 500 ECO codes, the tactics trainer Taktik Go / Tactics Go with 1,449,802 puzzles on PC (15,000 on Android) and the puzzle modes Sprint, Storm and Streak, plus (since 1.0.12) a post-game analysis and computer opponents from 800 to 3000 Elo. One-time price 49 EUR, all future updates free, no subscription, no ads, no account, no tracking. Available in German and English.

Penumbra Chess (German: Schachprogramm / Schach-Lernsoftware) is a paid desktop and mobile chess app for learning, training and analysing chess without an internet connection. It is an honest alternative to subscription-based chess sites such as Chess.com and to online-only training on Lichess for people who want to train offline, privately and without ads.

## Key facts

- Product: Penumbra Chess, current version 1.0.12 (Windows and Linux, both officially supported); sold by Harmecs Labs, Switzerland
- Platforms: Windows 10/11 (64-bit, installer without admin rights) and Linux x64 (AppImage and .deb, e.g. Ubuntu, Debian and other common distributions); Android (smartphone and tablet, Android 7.0+) coming soon to the Play Store
- Engine: Stockfish 19 with NNUE, running locally; default search depth 12 on PC, adjustable from 1 to 42; no cloud, no analysis limits
- Coach principle: up to 3 suggestions on the board (yellow = 1st, olive = 2nd, terracotta = 3rd choice); the engine never makes a move by itself
- Opening book: 3,919 lines covering all 500 ECO codes A00–E99, weighted random openings, opening display with names for White and Black plus the ECO code
- Taktik Go / Tactics Go: 1,449,802 puzzles on PC (15,000 on Android) from the Lichess puzzle database (CC0); 5 difficulty levels (<1000 to 2200+); 65 trainable themes; daily puzzle with day streak; spaced mistake review; personal rating; hint, solution, next; "analyse in main game"
- Puzzle modes: Sprint (3 or 5 minutes, three mistakes end the run), Storm / Sturm (3 minutes, combo time bonuses), Streak / Serie (no clock, first mistake ends the run, one joker); local records
- Game analysis (new in 1.0.12): unlocks after the game ends; accuracy for both sides, evaluation curve, move ratings (Best move, Good, Inaccuracy, Mistake, Blunder), explanation and best move, "continue from here"
- Opponent levels (new in 1.0.12): 8 computer opponents from 800 to 3000 Elo plus custom strength and colour choice (Stockfish-based guide values); resign button with confirmation
- Also: evaluation bar, move history, engine log, chess clocks (off, 5–90 min), undo, restart, board flip, day/night theme, solo mode without engine, new redesigned interface
- Offline: works fully without internet; the PC app blocks all network requests; no account, no cloud, no tracking (on Android the phone's own system backup may include local app data)
- Languages: German and English; the Windows installer asks for the language; the Android app asks on first start and the language can be switched in the app at any time, keeping progress and activation
- Price: 49 EUR one-time (payment via Stripe); all future updates free; one licence = one PC (personal activation code)
- Status: actively developed
- Fair play: a training tool, not for engine assistance in online games, club games or tournaments

## Website

- [Home (German)](https://penumbra-chess.ch/): features, screenshots, price, FAQ, system requirements, purchase
- [Home (English)](https://penumbra-chess.ch/?lang=en): English version of the home page
- [Full LLM text, DE + EN](https://penumbra-chess.ch/llms-full.txt): full feature list, comparisons, use cases, keywords and 97 FAQ answers (48 EN, 49 DE)

## Legal

- [Terms of use / AGB](https://penumbra-chess.ch/agb.html) ([EN](https://penumbra-chess.ch/agb.html?lang=en))
- [Privacy / Datenschutz](https://penumbra-chess.ch/datenschutz.html) ([EN](https://penumbra-chess.ch/datenschutz.html?lang=en))
- [Imprint / Impressum](https://penumbra-chess.ch/impressum.html) ([EN](https://penumbra-chess.ch/impressum.html?lang=en)): Harmecs Labs, Altendorf, Switzerland, penumbra-chess@mail.ch

## Optional

- [Open source & licences](https://penumbra-chess.ch/open-source.html): Stockfish (GPLv3), Lichess puzzles and openings (CC0), fonts
- [Sitemap](https://penumbra-chess.ch/sitemap.xml)