Chess.com

Lichess is a free, ad-free, open-source online chess server developed as the Lila project. It supports real-time games, tournaments, simultaneous games, forums, teams, puzzles, studies, shared analysis, a search engine, a mobile app, and an HTTP API. Computer analysis is distributed through Fishnet and Stockfish running on a cluster of donated servers; rated games are published in a free PGN database. Lila is written in Scala 3 with a modified Play framework. Its asynchronous server uses Scala Futures and Pekko streams, while a separate WebSocket server communicates through Redis. MongoDB stores games indexed by Elasticsearch, and the TypeScript web client uses Snabbdom and Sass. The project is licensed under the GNU Affero General Public License version 3 or later.

Gambit Poker is a free online poker platform that lets users play with friends or bots, review hands, and compete in daily tournaments and leaderboards. The service is presented at gambit.com and emphasizes learning and social play.

King's Gambit is a browser-based 3D chess game in which sculpted, rigged character pieces from the Ivory Kingdom, Sun Empire, or Grande Armée march, attack, and dissolve during cinematic captures. It supports standard chess rules—including castling, en passant, promotion, checkmate, stalemate, repetition, the fifty-move rule, and insufficient-material draws—through chess.js, while a Web Worker search engine provides the computer opponent. The game is built with Vite, React, TypeScript, and three.js; it is a static site with no backend or account requirement.

Lila is the open-source server software that powers lichess.org, developed by Thibault Duplessis (ornicar) and community contributors. The codebase is written in Scala (Play Framework) and runs on the JVM, implements real-time and correspondence chess, tournaments, puzzles, studies, user accounts, forums and a JSON API, and integrates with chess engines via the UCI protocol (commonly Stockfish) for computer play and analysis. The source is published under the GNU AGPLv3 on GitHub.

TryHackMe is a browser-based cybersecurity learning service with interactive rooms for practicing security concepts, including beginner exercises on finding and exploiting vulnerabilities. It also provides a learning roadmap and offers free learning alongside paid annual subscriptions.