Portal is a 2007 puzzle game in which the player uses a portal gun to create linked openings on walls and floors, moving through test chambers. Its key physics rule is that momentum carries through a portal, so a fall can be turned into a launch out the other exit. The player is guided by GLaDOS, a sarcastic AI who promises cake at the end. The game's mechanic was inspired by an earlier student game, Narbacular Drop, whose team was later hired by Valve.

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.