Detection

Awareness & Stealth

Stealth

A fight's first wave waits around the room unaware, wandering near where it started and sweeping a visible sight cone. Stay out of sight to pick your fights.

• Unaware cells show a tinted sight cone and a dim glow
• They see about 250 points inside a roughly 100° cone, and only with a clear line of sight
• They hear you all around within 85 points
• SPOTTED: a '!' appears and every unaware cell within 200 points is alerted in a chain
• A hunting cell that loses sight of you for 8 s gives up ('?') and wanders again; bosses, Killer T cells, summoned cells and Complement never give up, and in Endless Game Mode no cell does
• The first wave is spread in clusters across the room, never right next to you; reinforcement waves arrive already hunting

Ambush

2.5x damage

Catch a cell unaware and your shot hits much harder.

• Your auto-attack targets unaware cells only from 210 points (380 for hunting cells), so you sneak in close
• A hit on an unaware cell deals 2.5x damage and shows AMBUSH
• The hit alerts it, and it starts hunting you
• Killing an unaware cell raises Detection only half as much

Detection

Eye meter

The eye meter at the top right tracks how aware the immune system is of you, from calm green through yellow to pulsing red.

• Base points: a cell spotting you +3; each neighbour it alerts +0.5; every kill +1.2, plus 0.03 more for every kill this run (up to +3 more), half for cells a boss or another cell called in; getting hit +1; using your signature Shift ability +8 (Influenza A and Filovirus); a wrong step in a receptor puzzle +6; a Dendritic Cell's antigen presentation +18
• Every cell currently hunting you adds a little each second, plus a slow passive creep
• Never from the immune response itself: hunter squads, Immune Siege and treatment cells and Killer T cells (and anything they split or bud into) raise nothing, not by spotting you, hitting you or dying
• Fills 40% slower in the Nasal Passage and 20% slower in the Lungs than deeper in
• Colour: green below 50, yellow 50–74, red and pulsing from 75
• Cools off once nothing has raised it for 5 s and nothing is hunting you, then drains about 1.2 points a second, twice as fast while you stand still

Detection Thresholds

Escalation

Each section of the meter brings a bigger immune response.

• 35: first hunter squad
• 60: second hunter squad, bigger
• 75: the host may take a treatment (30% chance every 10 s)
• 80: third hunter squad, bigger still
• 100: Killer T cells are dispatched (from the Lungs on)
• A squad threshold re-arms only once Detection drops 20 below it

Hunter Squads

Reinforcements

Cytokines call in a squad of cells that already know where you are, through the door or corner farthest from you.

• Toast: IMMUNE RESPONSE · Cytokines have summoned a hunter squad
• Mostly neutrophils (4 + 1 per organ deep + 1 per squad already sent this run, sometimes one more) plus a B cell
• From the Lungs on: + a Macrophage
• From the Bloodstream on: + an NK cell and a clump of 3 platelets
• Every squad this run is bigger than the last, and gets tougher with Immune Alert
• Nothing a squad does raises Detection: spotting you, hitting you or dying

Cooling Down

Lower Detection

Ways to bring Detection back down and shake hunters off your trail.

• Refuge room: heals half your health, drops Detection by 30 and makes every hunting cell lose you (not bosses or Killer T cells)
• Solving a receptor puzzle: Detection -10
• Retrovirus's Latency: Detection -30 and hunters lose your trail
• Coming back from a Dormant Virion (extra life): Detection -25
• Destroying a Killer T pack: Detection drops to 0 and freezes for 20 s

Immune Alert

Run timer

A fever that rises one step every 20 seconds of the run (the flame number in the HUD), making the whole immune system tougher the longer you take.

• Each step: newly spawned cells get 6% more health and every hit on you is 4% stronger
• Boss base health +3% per step, Killer T base health +4% per step
• Raises elite odds (up to the equivalent of 2.5 extra organs at Alert 20)
• At Alert 3 the immune system starts learning your shot types

Fights in Waves

Waves

Fights come in waves: a big placed wave that starts unaware, then smaller reinforcement waves that pour in already hunting.

• Nasal Passage fights have 1 wave (2 deep in the organ); later organs 2 (3 deep in the organ); big rooms add one more and huge rooms another, up to 4
• Reinforcement waves are about 60% the size of the first and spawn away from you
• Every wave adds an antibody swarm on top
• A WAVE N / M pill shows progress