What did the e-Reader do for Pokémon?

The e-Reader is a Game Boy Advance accessory, a card reader that plugs into the cartridge slot and reads dot codes printed along the edges of specially made paper cards, loading data a stripe at a time. For Pokémon Ruby and Sapphire it acted as a side door into Hoenn, through which printed cards became content.

Its signature use hides in Mossdeep City. A locked door in one house opens to a trainer whose identity comes from the e-Reader Trainer cards the player scans, turning a card collection into a private battle facility. Berry cards worked the other direction, scanning in berries that Hoenn itself could not grow.

The system's most consequential card is documented on its own shelf in this cluster: the Eon Ticket, the magazine-distributed card that opened Southern Island. Around these headline uses sat a broader ecosystem of Pokémon e-Reader cards, promos and tie-ins that made 2003's paper hobby part of the video games.

The e-Reader itself had a short commercial life and a long shadow: it is the fullest attempt Nintendo ever made to merge its card business with its software, and its cards remain collectible precisely because each one is a tiny piece of software.