Mouser is an open-source, cross-platform (Windows, macOS, Linux) Logitech mouse remapper that serves as a local, telemetry-free alternative to Logitech Options+. It is a desktop application built with PySide6 and Qt Quick (QML) for the user interface, with platform-specific low-level mouse hooks (WH_MOUSE_LL on Windows, CGEventTap on macOS, evdev+uinput on Linux) to intercept and remap button presses and gestures. The core engine orchestrates per-app profile auto-switching, gesture recognition (swipe detection), a radial actions ring, DPI/SmartShift/haptic feedback control via HID++ protocol, and cross-platform shortcut injection. The application also includes an auto-updater, system tray integration, multi-language support (English, Simplified/Traditional Chinese), and a comprehensive test suite. While primarily a desktop application, it contains some research-like elements such as detailed HID++ protocol reverse engineering and a community-driven device catalog.