Level persistence

When you leave a room and come back, the game remembers most of what you did there. The room's state is saved the moment you leave and restored when you return. It is also written into your save file, so those changes survive even after you quit and reload.

What stays when you leave

• Destroyed and modified props. Broken pots, smashed crates, and other destructibles stay broken or stay in their changed state.
• Floor decals. Blood splatter, scorch and burn marks, footprints, and spent bullet and shotgun shells remain on the ground.
• Spilled fluids. Any water, oil, poison, or ice you created stays where you left it. See Fluids.
• Things you collected. Items you already picked up stay gone, opened chests stay opened, and collected key items stay collected.
• Burnt or destroyed foliage. Grass and similar plants remember if they were burnt.

What does not stay

• Dropped items. Any item lying loose on the ground disappears once you leave the room, so grab what you want before you go. This is deliberate: the game does not re-create dropped items when you return.
• Rooms flagged to reset. Some rooms are tagged to never persist (arenas, cutscene rooms, and similar). These reset to their original layout every time you enter.

Examples of things that persist

Thing	What it remembers
Grass (par_grass)	Whether it was burnt.
Breakable props (par_breakable)	Whether it was broken.
Destructibles (obj_destructible)	Its changed sprite and state.
Placed items (obj_prop_item)	Whether it was taken.
Chests (obj_prop_item_chest)	Whether they were opened.
Floor decals	Blood, burns, footprints, and shells.
Spilled fluids	The full fluid layout of the room.

How it works under the hood

Each room keeps a small "room data" record with a few parts:

• Modified room objects, such as grass and breakables, each storing a tiny bit of state (grass stores whether it is burnt, breakables store whether they are broken).
• Extra spawned objects, such as chests and destructibles, which are re-created from the record when you return.
• The fluid grid, a snapshot of every fluid tile in the room.
• The floor decals, baked into a buffer and stored with the room.

When you leave a room, its current state is snapshotted in memory. When you save the game, those snapshots are written to disk, one file per room, and returning to a room restores it. Objects that persist register themselves on room start and remove themselves if their saved state says they were destroyed.

Dropped items are the one thing the loader skips on purpose, which is why they vanish when you leave. Rooms tagged no_persist opt out of all of this and always reset to their original layout.