World War Z sales have piled up as fast as its mobs of zombies with close to two million units sold in just a month. Saber Interactive’s hit shooter launched April 16 and has enjoyed an overall warm reception from players and critics (here’s our review).

This latest sales milestone is the cherry on top of a month of good news. World War Z topped the UK charts shortly after its release. It has performed well on PC too, despite being an Epic Store exclusive. The third-person cooperative shooter borrows loosely from the 2006 novel of the same name and takes place in the same world as the 2013 film adaptation. Its narrative centers on a band of characters fighting to survive a zombie apocalypse across the cities of New York, Jerusalem, Tokyo, and Moscow. Taking inspiration from Left 4 Dead, up to four players work together to battle dense zombie waves numbering in the hundreds. The undead can even climb atop each other to reach higher areas just as in the movie.

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Publisher Focus Home Interactive states World War Z has already become one of their most successful titles to date. To celebrate, the team released an accolades video touting the game’s critical and commercial success.  They also promised more content to infect the game in the future, such as the previously announced new enemy type and additional Tokyo mission.

The post-launch roadmap of free updates will also include a six-skull difficulty setting, weekly challenge modes, and new cosmetic items for the already-addictive experience. A mysterious wave-based survival mode also waits in the wings. Down the line, players will gain the ability to swap classes during PvPvZ matches (which are two teams of players pitted against each other with zombies attacking both sides). Quality of life improvements to come include the introduction of private lobbies, Field of View, and level of detail sliders on PC.

Licensed games don’t often turn out great, making World War Z one of the year’s most pleasant surprises. Saber Interactive have honed in on not only what makes the IP work, but successfully tapped the still potent Left 4 Dead formula.

More: World War Z Is Too Much For These Streamers To Handle

World War Z is available now on PC, PlayStation 4, and Xbox One. For more information, visit the official website: https://wwzgame.com/