Stone Age Kings is a free browser strategy game that plays in a fanciful stone age. You begin as a small chieftain in your village and try over time to create an empire. You're playing with and against thousands of other Stone Age Kings players.
The game runs entirely in your browser and only requires the Flash plug-in from Adobe, which you will most likely already have, it's the same as the one need to watch videos on Youtube. Stone Age Kings runs even when you close the game and are no longer on the Internet. The bustle in your village goes on cheerfully, even if you do not intervene directly.
Source: The Game Website.