Each chamber becomes much harder than the last, with the final test taking place outside the official Aperture testing facilities. There are five official testing courses, each with a number of test chambers within, which will test both the robots' ability to solve the different puzzles as they progress.
The portals are capable of maintaining the flow of things, even if it enters a partner's portal, which is essential during some test chambers. Each bot comes equipped with their own Handheld Portal Device with separate portal colors.
Players take the form of two robot test subjects built by GLaDOS, Atlas the short and round blue bot, P-body the tall and pea-shaped orange bot that looks like a turret with arms and legs.
