A Fan-Made Browser Game Is Pro Pokémon Players' Secret Weapon kotaku.com

Around one million players a month are throwing down in Pokémon Showdown, a fan-made, browser-based game that recreates the battles found in official Pokémon games, with accurate stats.
Pokémon Crystal, released in Japan in 2000, was the first game to let players battle remote users with their cell phones.
In 2001, a group of fans from a Pokémon message board called Azure Heights created Porygon’s Big Show, which was at the time the only way to battle Pokémon remotely.
For starters, Pokémon Showdown offers players countless more ways to play than official Pokémon games do.
Sciarrone has nearly 200,000 YouTube subscribers, and about 80 percent of his uploads follow his competitive battles on Pokémon Showdown.