Picture, if you will, the opening scene of The Legend of Zelda: A Link to the Past. It’s storming outside. The princess is sending you telepathic messages asking if you’ll come save her. Your uncle leaves the house, telling you to stay put, and you go open the chest in your living room, expecting to find an old lamp. Instead you pick up the Power Glove, and suddenly you can pick up the rocks blocking your passage, allowing you to go explore the Eastern Palace before you’ve even gotten a sword.

Imagine: You’re playing Link to the Past, the seminal Super Nintendo action-adventure game, and you walk into a fortune-teller’s house, where you’d expect to find a soothsayer taking rupees in exchange for hints. Instead, the screen goes black for a few seconds. Suddenly you’re on Zebes, fighting aliens as a suited bounty hunter. Whoops, you’ve just walked into Super Metroid.