Freeciv is a nation-building strategy game in the vein of Civilization and Age of Empires that allows players to plan empires, design their structures, and iterate them endlessly within a dynamic and often punishing world.
The most obvious application is in a Social Studies or History classroom–accessibly game-based learning that allows students to directly participate in what amounts to be a conflict and historical learning simulation.
Up until now, the free and open-source title had to be installed on a local PC (or Mac) to work. Thanks to the devilry of technology, it is now compatible with HTML5, which means it can (probably) be played in your (Chrome or Safari) browser.
Head on over to the website and give it a shot–or, better yet, have students do that instead. An introduction and short tutorial appears below.