[One of 50 articles written and published for Demand Media in 2013]

Virtual worlds, like the real world, are set in a variety of environments. A variety of behavior is also possible in both realms — you can fight or socialize, plot strategy or play sports, dance or build a home. Virtual worlds encompass many of the behaviors we see daily in other media, both good and bad. For younger teens, some caution and parental guidance about the potential for manipulation and deception is advisable. Most of the worlds listed here are browser-based and free to play, although some require in-game purchases for complete access. Mac users can run PC games with a copy of Boot Camp.

Fight
Teenagers and combat environments go together like peanut butter and jelly. “Battlestar Galactica” is a war scenario that follows the same story line as the TV show. Pick a side, pick a ship and go to battle. In “Total Domination: Nuclear Strategy,” you’re in a world where a civil war is being fought, and you have to harvest resources, build forces and conquer all rivals to survive. “Offensive Combat” is rude, cartoonish and lots of fun, with fighting pandas and pistol-packing bananas. “Brick Force” is a mash-up with elements of “Super Mario,” manga, “South Park,” “Doom” and Lego. You get hilarious visuals, supreme silliness and the ability to easily build your own levels.

Love
Social games let you explore the virtual world, build, work together and do business. One of the oldest and best known is “Second Life.” The graphics are dated, but it’s a classic that continues to grow. “Planet Calypso” is a more modern, fully realized virtual world with a real economy. You can earn — and lose — real money in this world. “Grepolis” takes you back to ancient Greece. If you stay focused, you might be able to build Athens in a day. If dancing is your thing, head over to “5Street,” where you can dance on your own or put on a show with others. Finally, “Sims Social” is another classic game. You’ll need to visit Facebook to play it.

Learn
So you wanna be a doctor? In “Surgeon Simulator,” you can try your shaky, bloodstained hand at this amusing update to Operation. When you tire of exploring someone else’s inner space, switch over to outer space with “Celestia,” a realistic game that gives you the sun, the moon, Mars and the stars. For practice getting off Earth, there’s “Orbiter,” which puts you in the pilot’s seat of the space shuttle, the Apollo command module, lunar lander, Soyuz capsule and aboard the ISS. You can also join the Kerbal Space Program, build your own rockets, and test them against real-world limitations. If you prefer to stay closer to home, “X-Plane” is a flight simulator with a range of aircraft and airports to choose from. “X-Plane” and “Kerbal” are the only virtual environments in this group that aren’t free. Google Earth, the “GE Flight Simulator” and “Stellarium” are virtual representations of the real world. GE gives you the planet, Stellarium gives you the sky.

Play
Soccer fields are huge, but you can have your team do all the running for you. You play Perfect 11 Soccer in an impressively rendered stadium, and guide the action toward victory. Racing fans are in luck. Two browser-based Facebook racing worlds are available: “CSR Racing” and “Real Racing 3.” Buckle in, rev your engines and watch out for those curves. If you’ve got a mean curve ball, then wind up for the strikeout in “WGT Baseball: MLB.”