Massively multiplayer online crowdsourced games (MMOCGs) are very smart. I’m not sure of their specific history, but one of the first to become well known was Twitch Plays Pokemon. Another popular and innovative game that is currently ongoing is The Button. A cardinal feature of MMOCGs is the complex, emergent culture that they generate.
A new genre of video game!
The best of these surprise the player and keep her just barely constantly doing something.
An honorable mention, which doesn’t fit the browser criteria, is Little Inferno.
Updates as more good ones are made.
Accelerator is a brutal, high in tension, demanding of focus, and quite fun don’t-hit-the-walls game.
Kern Type is a kerning game, and the website author writes that more design games are in the works.