Anki is a mature, cross-platform spaced-repetition flashcard application. While it is fundamentally an end-user product, it contains significant embedded algorithmic and data-analysis components (FSRS memory-state scheduling, revlog analytics, retention simulation) that make it a hybrid of application and computational research. The production system consists of a Rust backend that owns all core logic, scheduling, SQLite persistence, sync, and media management; a Python Qt desktop frontend (`aqt`); a TypeScript/Svelte web UI for modern editors, graphs, deck options, and image occlusion; and a standalone sync server binary. Communication between languages is driven by protobuf service definitions, with generated bindings for Rust, Python, and TypeScript.
ProtonUp-Qt is a Linux desktop GUI built with PySide6/Qt6 for installing, updating, and removing Wine/Proton-based compatibility tools (GE-Proton, Proton-tkg, Wine builds, DXVK/VKD3D, SteamTinkerLaunch, Boxtron, Luxtorpeda, etc.) across Steam, Lutris, Heroic, Bottles, and custom launchers. Architecturally it is a client-side Qt application: the main window orchestrates background download/extraction jobs, a dynamic plugin loader (`ctloader.py`) discovers compatibility-tool modules under `resources/ctmods/`, and per-launcher adapters (`steamutil.py`, `lutrisutil.py`, `heroicutil.py`) read/write local game databases and config files. Release metadata is fetched from GitHub/GitLab/Codeberg REST APIs with rate-limit handling and optional user tokens. There is no server or data-processing component; external anti-cheat/compatibility datasets are only consumed to enrich the game-list dialog. The codebase demonstrates a credible plugin architecture, typed domain data in `datastructures.py`, and reusable network/download utilities. Maintenance is active, but the many tool-specific ctmods duplicate logic (fetch/install/extract), translations lag source strings, and the project depends on third-party release APIs and Steam's local formats, which makes some features inherently fragile.