Something has slipped past the skin. You are what the body sends back.

Active Immunity is a twin-stick bullet-hell roguelite fought inside the human body. Pick an immune cell, drop into infected tissue, and hold the line through 25 escalating waves of bacteria, viruses, fungi, parasites and worse. Weave through dense bullet patterns, stack upgrades into a build that feels unfair, and when the campaign is cleared, find out how long you last in endless.



Every cell has its own fire pattern, stats and special ability. Start as the Natural Killer Cell, and take each cell to wave 10 to unlock the next.

• Natural Killer Cell - a glass cannon that answers a crowd with a 20-bullet radial burst.
  
• T Helper Cell - support fire and a cytokine nova that clears the space around you.
  
• B Cell - antibody spreads and an opsonizing barrage: marked pathogens take 35% more damage.
  
• Macrophage - a tanky brawler that dashes straight through the swarm.
  
• Neutrophil - triple-shot fire and an extracellular trap that destroys enemy bullets.
  
• Dendritic Cell - a tactical debuffer whose antigen presentation boosts your damage 1.75x.

Every level-up is a choice. Draw from 54 upgrades across five rarities, from Common to Legendary, and max one out to unlock its evolution - 11 in all. Put the right pieces together and one of 23 synergies kicks in, turning a decent build into a screen-clearing one.





Eight pathogen families each fill the screen their own way: viruses that teleport and fire aimed spreads, fungi that release spores, tumours that split when they die, prions that spiral and shatter. Bosses arrive on waves 5, 10, 15, 20 and 25 - eleven of them, from the Viral Hydra to the Prion Cathedral, each with its own health phases and bullet patterns.

Before key waves, you choose how the outbreak mutates. Every choice is permanent and stacks, so each run gets harder in a direction you picked. Add run modifiers, encounter remixes and permanent contracts when you want more risk for more reward.

• The Complement System - a permanent tree of 30 skills across four branches, bought with fragments you earn every run. Fragments latch onto pathogens, and when one dies they seek out the next.
  
• Endless mode - keep going after the campaign, with milestones that change the rules as you go deeper.
  
• Daily runs, weekly objectives and seeds - same seed, same run. Share a run code and see who survives it longest.
  
• Practice range - try a cell and a build before you commit to a run.

Bring up to three friends into an online co-op run through Steam. Experience is shared, but every player levels up and picks upgrades on their own, and the outbreak scales with the size of your team.

Make the fight your own with the Steam Workshop: new enemies, cells, bosses, bullet patterns, upgrades and sounds. Modded runs keep their own progression, so your official save stays clean.

• Full controller support with Steam Input, plus keyboard and mouse; rebind any control
  
• Colorblind filters, high contrast, large text, reduced flashes, reduced motion and a screen shake toggle
  
• A guided tutorial for your first infection
  
• 36 Steam achievements and Steam Cloud saves
  
• English and Dutch