diff --git a/kiln-core/src/lib.rs b/kiln-core/src/lib.rs
index df4966f..a933753 100644
--- a/kiln-core/src/lib.rs
+++ b/kiln-core/src/lib.rs
@@ -6,6 +6,8 @@ pub mod game;
 pub mod log;
 /// Map file loading and saving (`.toml` format).
 pub mod map_file;
+/// World type: a named collection of boards in a single `.toml` file ([`world::World`], [`world::load`]).
+pub mod world;
 /// Rhai scripting runtime for board objects ([`script::ScriptHost`]).
 pub mod script;
 pub mod glyph;
diff --git a/kiln-core/src/tests/scripting.rs b/kiln-core/src/tests/scripting.rs
index 24c1c6b..afdc6ac 100644
--- a/kiln-core/src/tests/scripting.rs
+++ b/kiln-core/src/tests/scripting.rs
@@ -104,7 +104,8 @@ fn start_map_greeter_runs_init() {
     // confirm the greeter read the board (interpolated message) and wrote to
     // itself (set_tile). Also guards the example from drifting out of sync.
     let path = concat!(env!("CARGO_MANIFEST_DIR"), "/../maps/start.toml");
-    let board = crate::map_file::load(path).expect("load start.toml");
+    let mut world = crate::world::load(path).expect("load start.toml");
+    let board = world.boards.remove(&world.start).expect("start board");
     let mut game = GameState::new(board);
     game.run_init();
     assert!(
diff --git a/kiln-tui/src/main.rs b/kiln-tui/src/main.rs
index 1e337eb..3ec6713 100644
--- a/kiln-tui/src/main.rs
+++ b/kiln-tui/src/main.rs
@@ -19,7 +19,7 @@ mod input;
 
 use kiln_core::game::GameState;
 use kiln_core::log::LogLine;
-use kiln_core::map_file;
+use kiln_core::world;
 use ratatui::Frame;
 use ratatui::crossterm::event::{
     self, DisableMouseCapture, EnableMouseCapture, Event, KeyEventKind,
@@ -49,8 +49,14 @@ fn main() -> ExitCode {
     };
 
     // Load before touching the terminal so load errors print to a normal screen.
-    let board = match map_file::load(&path) {
-        Ok(board) => board,
+    let board = match world::load(&path) {
+        Ok(mut w) => match w.boards.remove(&w.start) {
+            Some(b) => b,
+            None => {
+                eprintln!("error: start board '{}' not found", w.start);
+                return ExitCode::FAILURE;
+            }
+        },
         Err(e) => {
             eprintln!("error loading {path}: {e}");
             return ExitCode::FAILURE;
diff --git a/maps/start.toml b/maps/start.toml
index 66d51dc..7ebb93d 100644
--- a/maps/start.toml
+++ b/maps/start.toml
@@ -1,10 +1,14 @@
-[map]
+[world]
+name = "Kiln Demo"
+start = "start"
+
+[boards.start.map]
 name = "Starting Room"
 width = 60
 height = 25
 player_start = "@"   # placed by the '@' grid char (convention)
 
-[palette]
+[boards.start.palette]
 " " = { archetype = "empty", tile = " ", fg = "#000000", bg = "#000000" }
 "#" = { archetype = "wall",  tile = "#", fg = "#808080", bg = "#606060" }
 "+" = { archetype = "banana", tile = "#", fg = "#808080", bg = "#606060" }
@@ -17,7 +21,7 @@ player_start = "@"   # placed by the '@' grid char (convention)
 # name the built-in generators (random dark, low-saturation texture cached at
 # load); a palette entry could also be a fixed glyph like
 # `{ tile = ".", fg = "#222", bg = "#000" }`.
-[floor]
+[boards.start.floor]
 content = """
 gggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
 gggggggggggggggggggggggggsgggggggggggggggggggggggggggggggggg
@@ -46,13 +50,13 @@ gggggggggggggggggggggggggsgggggggggggggggggggggggggggggggggg
 gggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
 """
 
-[floor.palette]
+[boards.start.floor.palette]
 "g" = "grass"
 "d" = "dirt"
 "s" = "stone"
 " " = { tile = "~", fg = "#6666ff", bg = "#000066" }
 
-[grid]
+[boards.start.grid]
 content = """
 ############################################################
 #                                                          #
@@ -83,7 +87,7 @@ content = """
 
 # Placed by its grid character `G` (uppercase-letter convention for objects)
 # rather than x/y; the cell under it loads as Empty.
-[[objects]]
+[[boards.start.objects]]
 fg = "#aa3333"
 bg = "#000000"
 palette = "G"
@@ -94,7 +98,7 @@ script_name = "greeter"
 # A solid object placed by x/y that paces east on its own. Demonstrates the
 # rate-limited move(), the blocked() collision check, the Queue object, and the
 # bump() hook (walk the player into it to trigger a bump).
-[[objects]]
+[[boards.start.objects]]
 x = 10
 y = 12
 fg = "#33aa33"
@@ -102,7 +106,7 @@ bg = "#000000"
 tile = 1
 script_name = "mover"
 
-[[objects]]
+[[boards.start.objects]]
 palette = "M"
 tile = 15
 fg = "#ffdd88"
@@ -112,7 +116,7 @@ name = "muffin"
 script_name = "muffin"
 
 # Notice board — long scroll to test overflow and scrolling.
-[[objects]]
+[[boards.start.objects]]
 palette = "B"
 tile = 240
 fg = "#cc9944"
@@ -121,7 +125,7 @@ solid = true
 name = "noticeboard"
 script_name = "noticeboard"
 
-[scripts]
+[boards.start.scripts]
 greeter = """
 fn init() {
     log(`hello from object — player at ${Board.player_x}, ${Board.player_y}`);
@@ -205,4 +209,4 @@ fn bump(id) {
         "  Unauthorised notices will be removed.",
     ]);
 }
-"""
\ No newline at end of file
+"""