The developers behind "World of Tanks: Xbox 360 Edition" often hear the same familiar line from Xbox owners who've downloaded and played the online tank combat game.

"They say, 'OK, this demo is great, but when is it actually coming out?' And we're like, 'No, you don't understand, it's a free game,' " said Mike McDonald, general manager of Wargaming Chicago-Baltimore in the West Loop. "And they're like, 'Wait, what do you mean it's free? Is there something wrong with it?' "

Don't worry, "World of Tanks: Xbox 360 Edition" isn't a digital Trojan Horse or a secret surveillance plot by the NSA. It's the first in a new wave of titles hitting home consoles that bypass the traditional way of buying games. Instead of running to the store and ponying up $60 for a physical box containing a disc to be slipped into an Xbox or PlayStation, users download the game directly to their system's hard drive and take the controls of a virtual World War II-era tank without spending a dime.

It's called free-to-play gaming, though the free part of the term comes with an asterisk. Players aren't forced to cough up money, but are strongly encouraged to make small purchases of in-game currency, vanity items, or, as is the case in "World of Tanks," additional vehicles and maps. It's a model that has dominated the PC, smartphone and tablet gaming market over the past several years. Two free-to-play computer games alone—"League of Legends" and "Dota 2"—accounted for a quarter of all PC gameplay time spent by the 28 million members of the video game social networking site Raptr in June. That's peanuts, however, compared to the 98 million users matching colorful candy on their mobile devices in "Candy Crush Saga."

Those are impressive numbers, but it's the mindboggling amount of cash that gamers have spent on microtransactions that have really lit up the eyes of game companies. "Clash of Clans" maker Supercell revealed in February that it made $892 million last year from a pair of smartphone and tablet games, and "Candy Crush Saga" developer King reported $1.9 billion in revenue in 2013—almost five times the earnings of box office hit "The Hunger Games: Catching Fire."

But Sony and Microsoft's home consoles remained immune to the charms of free-to-play when Cyprus-based game developer Wargaming approached Chicago's Day 1 Studios in mid-2012 about the possibility of bringing its popular "World of Tanks" PC game to the Xbox 360. Day 1, who previously worked on the "MechAssault" series, impressed with its ability to switch gears from games about giant weaponized robots to armored fighting vehicles, so much so that Wargaming purchased Day 1 in December 2012 for a reported $20 million and renamed it Wargaming West. (It has since been renamed Wargaming Chicago-Baltimore.)

Since then, Wargaming Chicago-Baltimore has worked exclusively on "World of Tanks: 360 Edition," despite the fact that the game was officially launched in February. The studio continues to fix bugs and introduce monthly updates with bonus features. It recently introduced weather patterns so players can steer their steel behemoths through driving rain or snow, and a Fourth of July promotion added a red, white and blue Freedom Tank into the mix of 240 different vehicles.

Some of the changes are based on player demands, others are the result of an analytics team located in Austin, Texas, that Wargaming employs to parse nearly every shot fired or virtual mile driven. The programming team uses that information to tweak the game accordingly.

"The coolest thing now is getting to see the customers' response immediately and then you can do stuff about it," said Denny Thorley, Wargaming Chicago-Baltimore SVP of product development. "And so it's kind of a process of, OK, this is what we think players are doing, this is what they're saying on the forums that they're doing—but then this is what they're actually doing. It's incredibly helpful."

Wargaming Chicago-Baltimore senior sound designer Brendan Blewett said he can't imagine going back to the old way of making games.

"Traditionally, you've had this boxed copy of a game, where you have a deadline, and then you put it out and cross your fingers and hope it's good," Blewett said. "But this is pretty cool, because it's like being able to change a movie after it's released. This is more of a service than a product."

The jury remains out, however, on the possibility of "World of Tanks: 360 Edition" or its free-to-play console competitors matching the success of some of the heavy hitters on PC and mobile platforms.

"Thus far, it's not taking off as a revenue model for console," said Dennis Fong, CEO of Raptr. "The leading examples are 'DC Universe' and 'World of Tanks,' but they're the exception, not the rule, on console."

"It's still a foreign concept to a lot of people," Wargaming Chicago-Baltimore executive producer TJ Wagner said. "They can't go down to Best Buy or wherever and buy it, so they don't really know about it. Digital distribution is still something that's still brand-new."

Wargaming wouldn't reveal the amount of cash that players have invested in "World of Tanks: 360 Edition," but Thorley pointed to one important metric that indicated the health of the game: the growing number of jobs at the studio.

"We've been growing like crazy. We were at like 36 people in December 2012, we're about 130 people now and we're hiring 50 or more people [within the next] year," he said. "So yeah, we're pretty optimistic and we're going to continue to grow as the demand for the product continues to grow."

>>World of Tanks: Xbox 360 Edition statistics to date:
14+ million battles
3.8+ million downloads

Ryan Smith is a RedEye special contributor. redeye@tribune.com | @redeyechicago