thorium-reader

Agora Flat provides web and desktop clients for creating, joining, and scheduling online classrooms. Teachers and participants can combine an interactive whiteboard with live audio, video, messaging, screen sharing, and course materials, then replay recorded classroom activity. The open-source client may be used commercially, but the project does not provide commercial customization, deployment assistance, or customer support.

Piano Trainer turns scales, chords, and the circle of fifths into interactive desktop exercises. Learners can respond with a MIDI keyboard or the computer keyboard, then reinforce recall through quizzes, hard mode, and shuffled practice. Free cross-platform builds are available. It works best as a hands-on reference and repetition tool for self-paced learners rather than as a complete structured piano course.

En Croissant is a cross-platform chess GUI for storing and analyzing games from Lichess and Chess.com. It supports multiple UCI engines, simplifies engine and database management, and can search a game collection for exact or partial positions. Players can also build an opening repertoire and train it with spaced repetition. The result is a single desktop workflow for post-game analysis, position research, and repeated opening practice.

MarkerOn lives in the system tray and opens a screen-wide annotation layer with a global shortcut. Draw, highlight, add arrows, shapes, or text, then enable click-through mode to keep the marks visible while interacting with the application underneath. It also includes a whiteboard, image copying, and optional drawing persistence. The roughly 1.5 MB desktop app supports Windows, macOS, and Linux.