Cookie Clicker is a popular browser game about clicking cookies, automating the production of cookies, and relishing the acquisition of millions of virtual cookies. Along with Candy Box, it's one of the games that helped popularise the idle game genre. Both succeeded for fairly obvious reasons: one was about accruing lots of cookies, the other was about accruing lots of candy.
Cookie Clicker is getting a Steam release on September 2. Or, you could just click here and play it. The game has been in active development since 2013, but it's still fundamentally the same. The player starts with a single click of a cookie, which grants them one (1) cookie. If they click the cookie again, they have two (2) cookies, and so on, until they've clicked the cookie enough times to unlock less laborious ways of generating cookies. These include grandmas that bake cookies en masse, and even time machines that drag cookies from the past and future into the greedy cookie-coveting present. If you love to watch numbers go up in MMOs, Cookie Clicker basically strips away all the superfluous thinking and dexterity you'd normally associate with "gameplay".
The Steam version appears to be the culmination of eight years of work for developer Orteil. When it launches it'll do so with 600+ upgrades and music by C418 of Minecraft fame. Most importantly—and probably the reason some will opt for Steam over the extremely easy-to-access browser version—is the over 500 Steam achievements included, which should make it easier to show friends how many cookies you've clicked. Cloud saves should help avert disastrous loss of cookies, too.
Back when Cookie Clicker and Candy Box first released they were seen as (possibly inadvertent) critiques of grind-based MMO gaming. But the genre has prospered on Steam: Get a load of how many games the 'idler' tag brings up nowadays.