Portal

A sci-fi puzzle video game series telling the story of a woman named Chell and her experiences as a test subject for Aperture Laboratories. During her time as a human lab rat, she solves test chambers (areas designed to be puzzles) with the aid of the Aperture Science Handheld Portal Device, more commonly known as the Portal Gun. The one overseeing her testing is a giant machine known as GLaDOS who provides guidance on newly-entered chambers when appropriate. Portal (published 2007) and Portal 2 (published 2012) were both released on Steam for purchase.