This repository provides the firmware and desktop tools for Petoi's quadruped robots (Bittle, Nybble, Chero). The core is an Arduino-based firmware (OpenCat.ino) running on ATmega328P (NyBoard) that handles servo control, gait generation, IMU integration, sensor processing (IR, ultrasonic, gesture, voice), and skill execution via pre-programmed motion sequences. A Python desktop application (pyUI) offers firmware upload, joint calibration, skill composition, and debugging. A Python serial API (serialMaster, OpenCatPythonAPI) enables scripting robot behaviors. The architecture is monolithic firmware with conditional compilation for multiple hardware variants and sensor options. While the project has a large user base and extensive documentation, the codebase shows signs of technical drift: it is explicitly legacy (development moved to OpenCatESP32), relies on outdated libraries, has duplicated code (e.g., three copies of IRremote), and uses global state and hardcoded paths. The skill system and serial protocol are well-defined patterns, but overall reusability is limited by tight coupling to specific hardware and board versions.