With a word salad title like PlayerUnknown's Battlegrounds, you might be forgiven for not immediately grasping what the game is about.

At first glance, it doesn't look like anything special: an online shooter set on a generic abandoned island with few distinguishing details other than the occasional Soviet-style architectural flourish.

But Battlegrounds is the best distillation of a new genre of shooter — the "last-man-standing shooter" — which takes inspiration from the Japanese film Battle Royale or its American counterpart, The Hunger Games, and is widely credited to a single developer, Brendan Greene (a.k.a. PlayerUnknown).

It's also been the best-selling game on PC retailer Steam since it launched in April, making Greene and Korea-based developer studio Bluehole Inc. an estimated $46 million in its first month alone.

This success has come without much traditional marketing to speak of — no TV commercials or print advertisements and no physical disc release in stores.

So what's behind its meteoric rise to popularity?

Inspired by Battle Royale, Hunger Games

The rules of PlayerUnknown's Battlegrounds (PUBG for short) are simple.

Up to 100 players are loaded onto a cargo plane that drops them with a parachute and nothing else over an eight-square-kilometre island.

Players must scramble to find armour, weapons and other equipment to defend themselves and kill the competition. The last player alive is the winner.

The genius of Battlegrounds is how it pushes surviving players together as the number of competitors dwindles.

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Battlegrounds' central tension comes from wide open areas and the constant threat of being in an opposing player's sights. (Bluehole, Inc.)

Every few minutes, an electric "wall of death" constricts the play field and anyone caught on the wrong side of it is killed. Survivors are thus forced into an inevitable showdown — they can't sit idly by, hoping no one notices them.

To make things even more tense, at regular intervals, random areas of the island are bombed from above, forcing players to either flee the region or scramble for cover inside a building — which might be occupied by another hostile player.

Battlegrounds wears its cinematic inspirations on its sleeve. Greene's first take on the genre was a fan project — or "mod" — that added the mode to existing games such as Arma 3 and H1Z1. He called the Arma 3 mod "Battle Royale," to avoid any confusion.

Unlike his previous work, Battlegrounds was built from the ground up with the Battle Royale format in mind. Players and critics have praised it for refining the previous project's ideas into a coherent experience that strikes the right balance between accessibility and breadth of strategic options available.

More horror than action

Unlike more traditional multiplayer shooter games like Call of Duty or Overwatch, you don't re-enter the match after you die. Once you're dead, you're flung back onto an online lobby to re-board the cargo plane and try again from the start, with a new crop of would-be murderers.

Every move becomes a precarious gamble. Running down an open road risks putting you in the sights of an enemy. And firing your weapon risks alerting players to your position.

In the top-right corner of the screen, a counter tracks the remaining number of players. As that number ticks down from 100, you're made constantly aware of players being picked off, with the reminder that you could be next.

It is a shooter with the soul of a horror game.

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Battlegrounds' abandoned island doesn't look special at first glance, but it affords plenty of tactical options for imaginative players. (Bluehole, Inc.)

"This is the power of PlayerUnknown Battlegrounds. The tension, the waiting, the miserable slow crawl through fields as you scan the pixelated horizon for movement," writes Wired's Julie Muncy.

"In a landscape where most competitive multiplayer games are about complexity, fast play, and high player engagement, Battlegrounds is willfully sprawling and anxious."

Preview version popularity

Battlegrounds is currently listed on Steam as being in "Early Access" mode, meaning it's not technically finished. Greene and Bluehole have been updating the game regularly since it went on sale, ironing out bugs and adding features as requested by players.

Indeed, the game's glitchy, ramshackle nature has become part of its appeal.

Using a motorcycle helmet to protect your cranium in the absence of military headgear, or deflecting a sniper's bullet with a cast iron frying pan, can be just as memorable as winning a match.

But every so often, players will run into glitches that lead to an unforeseen yet comically absurd setback. Sometimes you'll jump out of a boat or buggy, only to be clipped and knocked over because you didn't time your exit properly.

Other times, entire houses or buildings fail to load on the screen, making it seem as if other players walking on upper floors are flying through the air.

Moments like that elicit gasps and groans from players livestreaming their game on Twitch, to the anguish or delight of those watching (and typing their own reactions into the live chat).

Bluehole estimates Battlegrounds will graduate from its Early Access mode to a "final" release in about six months.

Given the game's astonishing popularity even in its unfinished state, it's easy to predict that its best and most profitable days are still ahead.