Bulletstorm is a free-to-play zombie FPS survival shooter by Ryki Studio, built in HTML5 Unity WebGL, where you dual-wield dozens of firearms and mow down screen-filling undead hordes. It blends first-person shooting, tower-defense positioning, and roguelike upgrades, with over 50 weapons, a roster of heroes, and massive boss encounters.

It runs directly in the browser on desktop, mobile, and tablet, and also has official iOS and Android apps from the developer as well as a CrazyGames App build. PLRun availability is not confirmed in the sources reviewed, so treat the browser build on CrazyGames as the primary free-access path.

Bulletstorm is a horde-survival FPS with tower-defense framing: you stand your ground, aim at oncoming zombies, and scale your firepower across a run rather than exploring a traditional level. The official Google Play listing describes wielding up to six weapons simultaneously, which is the defining mechanical hook.

The core loop is survive a wave, pick up roguelike upgrades or loot drops, recruit and level heroes, and push into tougher waves and boss encounters. Unpredictable loot and upgrade paths mean no two runs play out the same, which is where the "can't stop playing" incremental feel comes from.

It suits players who like horde shooters such as Vampire Survivors or Call of Duty Zombies distilled into short, arcade sessions — high enemy density, fast feedback, and a clear dopamine curve of bigger guns and bigger numbers. You defend a position against escalating zombie waves by firing multiple weapons at once, collecting loot, and upgrading between or during waves.