With 4.5 million players, Dota Auto Chess is turning into a gaming sensation.

Of course, that depends on how exactly you define Auto Chess: Is it a game, a mod, or “a mod of a remake of a mod based on a map from another game”?

Whatever it is, Dota Auto Chess is a strategy game made by Drodo Studio in China. The game essentially consists of two phases. First is the preparation round, where you pick heroes to assemble an army, and then place them on the board. After that is the battle round, which is where the “auto” in auto chess comes from -- all you can do is sit back and watch your army take on your opponent, and hope that you set everything up properly in the preparation round.

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If you think you’ve heard of something before, you’re not alone. People have been pointing out the resemblance between Dota Auto Chess and various Warcraft III custom maps, like the (unofficial) Pokémon Defense or Fighting the Three Kingdoms in China.

One of the big differences is in how you set up your team in Dota Auto Chess.

Given that you can’t do anything but watch in the battle round, the preparation round is critical to success. With each unit having its own unique abilities, it would seem logical to select a team that has a wide range of skills to counteract anything that your opponent has.

And here’s where Dota Auto Chess makes life harder: It gives players incentives to have less variety in their teams. For instance, if you have four orcs on a team, they will individually have more health than if you just deployed a single orc. And if you have multiple of the same hero, they can merge into a singular, more powerful version of that hero.

Drodo Studio has experience here, as their last game -- Gem TD, a custom map for Warcraft III -- also used merging mechanics.

There’s another inspiration for these mechanics, and it’s also an older game. Much, much older: Mahjong.

The developers say that they’ve incorporated many elements of the ancient Chinese tile-based game (which happens to be Mao Zedong’s favorite) in Dota Auto Chess. The merging mechanic I mentioned before? That’s inspired by mahjong, which rewards players for playing three of the same tile.

Each hero in Dota Auto Chess also belongs to both a species and a class -- like Puck, who happens to be a dragon, elf and mage all at once. That’s similar to mahjong, where tiles have both a number (say, one) and a suit (like bamboo). To win in both games, having the right combination of those attributes is crucial.

While writing this story in February 2019, Dota Auto Chess had more than 150,000 concurrent players at any given point of the day. (Picture: Valve)

And since there are only a limited number of tiles in mahjong or heroes in Dota Auto Chess, grabbing the right ones from the pile is critical. Both games require players to pay attention to what their opponents draw and figure out how best to counter them -- and how to prevent them getting other good tiles or heroes.

This is where the strategic fun of these two games comes from: How do you quickly assemble a winning hand while sabotaging your opponents before the battle even begins?

Despite being called “a reskin of mahjong” by some Chinese media outlets, the two games do have significant differences. Mahjong is a game of speed, while Dota Auto Chess is about power. The latter is all about battles, while the former is about being the fastest to assemble a winning hand.

Another key difference is that, while all tiles are created equal in mahjong, some heroes in Dota Auto Chess are better in the early game or late game. There’s an economy system, like Dota, which gives the game a sense of progression. Some heroes are more powerful, but cost the player more to draft -- so they might not be worth it in the early rounds.

Those elements from real-time strategy games shows how effective this game is as a hybrid, taking elements from those modern games and fusing it with a bit of mahjong. Considering how both have plenty of fans, maybe it’s not surprising that a fusion between them works so well.

(On the other hand, maybe not all mash-ups are meant to be.)

If you want to check out more of Dota Auto Chess, watch our full stream here!