Cookie Clicker was created in 2013 by French developer Julien "Orteil" Thiennot, originally as a small side project, and went on to become arguably the single most influential game in the incremental/idle genre. Its premise couldn't be simpler β click a giant cookie to earn cookies, spend them on cursors, grandmas, farms, and increasingly absurd cookie-production buildings β but that simple loop, combined with a steady drip of achievements, upgrades, and eventually a whole hidden narrative layer, turned it into a genre-defining phenomenon that inspired an entire wave of "clicker" games that followed.
What made it stand out beyond its mechanics was its sense of humor and scale β the numbers involved eventually grow into the astronomically large, and the game leans into that absurdity with self-aware achievement names and easter eggs rather than taking its own premise too seriously.
There's no traditional ending β the entire point is the open-ended climb, watching your cookies-per-second grow from a trickle into an overwhelming flood, with achievements and milestones marking progress along the way rather than any final victory condition.
It's the game that essentially created the modern idle genre, and it remains one of the most polished, funniest examples of it more than a decade later. GBK Games also has Clicker Heroes and AdVenture Capitalist for more of that same genre.