The run is a stack of floors
A run is a chain of floors stacked one above the other. You begin on the first basement floor and descend from there.
Each floor is a small grid of rooms hidden in fog. You reveal rooms by walking into them, one move at a time.
The goal on every floor is the trapdoor or hatch. That exit drops you to the next part of the run.
Clearing a room
Most rooms hold enemies. The doors lock while enemies live, so you must clear the room before you can leave.
Clearing a room can drop pickups, a chest, or nothing at all. Some rooms hold an item pedestal instead.
Item rooms give a free item, but only if you can reach them and only once per floor.
What a floor contains
A floor hides a set of special rooms. These include the item room, the shop, the boss room, and often a secret room.
The boss room guards the exit. Defeat the boss and a trapdoor opens, or it appears in the middle of the room.
Bosses can also shift your Devil or Angel room odds. Your choices on the floor shape what appears later.
Going deeper
Depth raises the stakes. Enemies hit harder, and rooms fill with more of them. Health becomes the resource you guard.
Death ends the whole run. There is no checkpoint and no retry from the same floor.
Spend pickups before you descend. A coin or key you carry down is one you did not use on the floor that needed it.
Next: Floor routing and Keys, bombs and pickups.