The premise is simple, but it can get addicting later on, leaving the tab open to accumulate mass amounts of doughy goodness.
There are also upgrades that double certain cookie gatherers Cookies per Second, and even achievements that increase your Milk.
There are updates almost daily as well, bringing in new gatherers, or a new upgrade.
----------
Cookie Clicker
Cookie Clicker Classic
Clicking Bad (Aka, Meth Clicker)
----------
If you are on a low-end computer, turn off Milk, Particles, and Numbers in the Menu.
The game will run much faster.