gaia is the user interface of firefox os and controls everything drawn to the screen. gaia includes by default implementations of a lock screen, home screen, telephone dialer and contacts application, text-messaging application, camera application and gallery support, plus the classic phone apps: mail, calendar, calculator and marketplace. gaia is written entirely in html, css, and javascript. it interfaces with the operating system through open web apis, which are implemented by gecko. because it uses only standard web apis, it can work on other oses and other web browsers.