Termux-OS is a menu-driven shell customization tool for Termux that enables users to install and configure shells (zsh, fish, bash) with themes, fonts, and security features. The core functionality is implemented in a single bash script (os.sh) that presents an interactive menu for installing shells, applying color themes, setting up a cyber lock (password protection via SHA-256 hashing), configuring terminal behavior, and updating the script. The architecture is monolithic but modularized into functions for each major task. Key external dependencies include git, curl, pkg, and various fonts/shell frameworks. The script writes configuration files to user directories (e.g., ~/.bashrc, ~/.zshrc, ~/.termux/properties) and downloads resources from GitHub.