Each organ is a branching map of connected rooms, generated fresh every run: different layout, room count, room sizes and mix of room types. Beat the boss at the far end to descend to the next organ, all the way from the Nasal Passage to the Brain.
Most rooms are fights, and they come in many sizes and silhouettes, some sprawling past the screen.
Sizes are picked from 1×1 screen up to 2.2×1.8 screens, plus narrow corridors (2.4×0.55 and 0.62×2.0); then each room shrinks to fit its first wave, never below half a screen of floor or 0.6 of a screen on a side (a corridor only gets shorter, never under a screen long)
Shapes: L, T, U, C, H, Z and S bends, crosses, stairs, rings, octagons, notched rooms and rooms with one or two islands of tissue, picked to suit the room's doors and size; about 1 in 6 stays a plain rectangle, and narrow corridors always do
About 45% (not corridors) have 1–2 inner walls, bars of tissue across the floor (up to 3 in big rooms); tissue nodules give cover
Islands (a ring room has one in the middle) and inner walls are raised mounds of the organ's own tissue that block you, cells and shots; an octagon's corners are cut on the diagonal, and you and cells bump into the diagonal itself
Clear lanes always run from every door to the middle (a ring room's island sits there, and you walk round it); a shape never leaves a gap narrower than 96 points, so even the biggest cells get through, and islands keep a 90-point walkway all round
Fight rooms count toward the "x/y fights" progress shown on the HUD
In Pandemic Game Mode, Sydney's Bondi Beach Reopens makes every room a plain rectangle with no inner walls (boss and special rooms too), and Mexico City's Metro Line 1 Rush Hour makes every fight room a narrow corridor
From the Codex
Each organ is a map of connected rooms, different every run.
Fun fact: Bigger rooms hold more cells, spread around the whole room, and always fight in several waves.
Doors seal while anything is hunting you and stay sealed between waves until the room is cleared.
Boss rooms stay sealed until the boss dies; Immune Siege and Lysis Chamber stay sealed while their timers run
Tumor rooms never lock, so you can always walk away from a cancer
Every doorway is a sphincter in the wall: open, it's dilated into a ring with light from the next room beyond; sealed, it clenches into a tight red, veined membrane that throbs, its light turns red, and you stop just in front of it
An open door glows in the colour of the room beyond it: fight rooms mint, boss orange, Mutation Chamber gold, puzzle blue, altars and Mutagenic Pool purple, Gene Chamber teal, Siege red, Lysis Chamber amber, Refuge green, tumor pink
From the Codex
Each organ is a map of connected rooms, different every run.
Fun fact: Bigger rooms hold more cells, spread around the whole room, and always fight in several waves.
Beat the organ's boss to open a passage to the next organ; you're asked to confirm, because there's no coming back.
The boss room is drawn double-size on the minimap with a skull
The arena is a plain hall or, half the time, an octagon with its corners cut, with 0–2 tissue nodules for cover: 1.35×1.35 screens in the Nasal Passage, 1.6×1.5 elsewhere (some Pandemic Game Mode cities resize it)
Beating the boss drops a named gear set piece (an ordinary piece of the same tier in Pandemic Game Mode) and Chaperone Proteins, with a chance of a Dormant Virion (never from the Brain's boss), and leaves a mutation orb unless the run ends there
The prompt warns how many rooms are still unexplored
Descending heals 50% of max HP
Beating the Brain's boss, the Microglia, wins the run: the host is fully infected
From the Codex
The giant immune cell guarding the way to the next organ.
Fun fact: From the third organ on, every boss also has a signature skill on its own random clock, aimed at you.
