From 03185c9c688dbdd516e56a92a78b9de9086fbcfe Mon Sep 17 00:00:00 2001
From: Ross Andrews <ross.andrews@gmail.com>
Date: Sat, 11 Jul 2026 14:47:08 -0500
Subject: [PATCH] lighting

---
 kiln-core/src/action.rs             |   4 +
 kiln-core/src/api/object_info.rs    |   8 ++
 kiln-core/src/archetype.rs          |  29 +++++
 kiln-core/src/board.rs              | 144 ++++++++++++++++--------
 kiln-core/src/fov.rs                | 163 +++++++++++++++++++++++-----
 kiln-core/src/game.rs               |  12 ++
 kiln-core/src/layer.rs              |   7 ++
 kiln-core/src/lib.rs                |   4 +-
 kiln-core/src/map_file.rs           |   3 +
 kiln-core/src/object_def.rs         |   6 +
 kiln-core/src/script.rs             |   7 ++
 kiln-core/src/tests/game_portals.rs |   1 +
 kiln-core/src/world.rs              |  12 ++
 kiln-tui/src/main.rs                |   8 +-
 kiln-tui/src/render.rs              |  74 ++++++++++---
 kiln-tui/src/speech.rs              |  14 +--
 maps/dark.toml                      |  17 ++-
 17 files changed, 408 insertions(+), 105 deletions(-)

diff --git a/kiln-core/src/action.rs b/kiln-core/src/action.rs
index 759a8a8..0a24176 100644
--- a/kiln-core/src/action.rs
+++ b/kiln-core/src/action.rs
@@ -72,6 +72,9 @@ pub enum Action {
     Move(Direction),
     /// Set the source object's glyph tile index.
     SetTile(u32),
+    /// Set the source object's light radius in cells (0 = no light). Zero time
+    /// cost. Applied to the source [`ObjectDef::light`](crate::object_def::ObjectDef::light).
+    SetLight(u32),
     /// Add (`present = true`) or remove (`present = false`) `tag` on `target`.
     SetTag {
         target: ObjectId,
@@ -131,6 +134,7 @@ impl Debug for Action {
         match self {
             Action::Move(dir) => write!(f, "Move({:?})", dir),
             Action::SetTile(i) => write!(f, "SetTile({i})"),
+            Action::SetLight(r) => write!(f, "SetLight({r})"),
             Action::SetTag { .. } => write!(f, "SetTag"),
             Action::Say(_, _) => write!(f, "Say"),
             Action::Delay(t) => write!(f, "Delay({t})"),
diff --git a/kiln-core/src/api/object_info.rs b/kiln-core/src/api/object_info.rs
index 59fc683..d68f849 100644
--- a/kiln-core/src/api/object_info.rs
+++ b/kiln-core/src/api/object_info.rs
@@ -113,6 +113,14 @@ impl Registerable for ObjectInfo {
             obj.glyph
         });
 
+        // me.light: the object's current emitted light radius in cells (0 = none).
+        engine.register_get("light", |o: &mut ObjectInfo| -> i64 {
+            match o.board.borrow().objects.get(&o.id) {
+                Some(ObjectDef { light, .. }) => *light as i64,
+                None => 0,
+            }
+        });
+
         engine.register_fn("has_tag", |o: &mut ObjectInfo, t: String| {
             if let Some(ObjectDef { tags, .. }) = o.board.borrow().objects.get(&o.id) {
                 tags.contains(&t)
diff --git a/kiln-core/src/archetype.rs b/kiln-core/src/archetype.rs
index cb472af..1669361 100644
--- a/kiln-core/src/archetype.rs
+++ b/kiln-core/src/archetype.rs
@@ -184,6 +184,9 @@ pub enum Archetype {
     HCrate,
     /// A crate that can only be pushed north/south (vertical axis). Glyph ↕.
     VCrate,
+    /// A wall-mounted torch: non-solid, non-opaque decorative terrain that emits
+    /// warm light on a `dark` board (radius from [`Archetype::light`]). Glyph ☼.
+    Torch,
     /// A script-backed archetype expanded from a map-file keyword.
     ///
     /// - `Builtin` is the family (e.g. `Builtin::Pusher`), which selects the
@@ -234,6 +237,13 @@ impl Archetype {
                 pushable: Pushable::Vertical,
                 grab: false,
             },
+            // A torch you can walk past and see through; it only lights the room.
+            Archetype::Torch => Behavior {
+                solid: false,
+                opaque: false,
+                pushable: Pushable::No,
+                grab: false,
+            },
             Archetype::ErrorBlock => Behavior {
                 solid: true,
                 opaque: true,
@@ -252,10 +262,23 @@ impl Archetype {
             Archetype::Crate => "crate",
             Archetype::HCrate => "hcrate",
             Archetype::VCrate => "vcrate",
+            Archetype::Torch => "torch",
             Archetype::ErrorBlock => "error_block",
         }
     }
 
+    /// Light radius in cells this archetype emits on a `dark` board (0 = none).
+    ///
+    /// The emitted *color* is the cell's glyph foreground color (see [`crate::fov`]).
+    /// Only `Torch` glows today; everything else is dark. Script-backed builtins
+    /// carry their light on the expanded [`ObjectDef::light`] instead.
+    pub fn light(&self) -> u32 {
+        match self {
+            Archetype::Torch => 6,
+            _ => 0,
+        }
+    }
+
     /// Returns the default glyph painted when the editor stamps this archetype.
     ///
     /// This glyph is used only for new cells created in the editor; existing
@@ -289,6 +312,11 @@ impl Archetype {
                 fg: Rgba8 { r: 0xAA, g: 0xAA, b: 0xAA, a: 255 },
                 bg: Rgba8 { r: 0, g: 0, b: 0, a: 255 },
             },
+            Archetype::Torch => Glyph {
+                tile: 15, // CP437 ☼ (sun) — a warm point of light
+                fg: Rgba8 { r: 0xFF, g: 0xB0, b: 0x40, a: 255 }, // warm amber (also its light color)
+                bg: Rgba8 { r: 0, g: 0, b: 0, a: 255 },
+            },
             // Visually distinct so malformed map files are immediately obvious.
             Archetype::ErrorBlock => Glyph {
                 tile: 63,
@@ -319,6 +347,7 @@ impl TryFrom<&str> for Archetype {
             "crate" => Ok(Archetype::Crate),
             "hcrate" => Ok(Archetype::HCrate),
             "vcrate" => Ok(Archetype::VCrate),
+            "torch" => Ok(Archetype::Torch),
             // "object", "portal", "player" are intentionally absent: they are
             // meta-kinds handled by the layer builder, not Archetype variants.
             _ => Err(format!("unknown archetype: {name}")),
diff --git a/kiln-core/src/board.rs b/kiln-core/src/board.rs
index 4518df3..c4b3414 100644
--- a/kiln-core/src/board.rs
+++ b/kiln-core/src/board.rs
@@ -1,8 +1,7 @@
 use crate::archetype::Archetype;
 use crate::floor::Floor;
-use crate::fov::{SIGHT_RADIUS, Visibility};
+use crate::fov::{FovCaster, Lighting, color_to_rgb};
 use crate::glyph::Glyph;
-use doryen_fov::{FovAlgorithm, FovRecursiveShadowCasting, MapData};
 use crate::log::LogLine;
 use crate::object_def::ObjectDef;
 use crate::utils::Direction;
@@ -104,9 +103,9 @@ pub struct Board {
     /// rather than being tied to a specific object cell. Scripts live in
     /// [`World::scripts`](crate::world::World) and are looked up by this name.
     pub board_script_name: Option<String>,
-    /// When `true`, this board is "dark": front-ends reveal only the cells
-    /// within the player's field of view (see [`Board::player_fov`]) and draw
-    /// everything else as unlit darkness. Sight is blocked by opaque cells.
+    /// When `true`, this board is "dark": front-ends reveal only the cells the
+    /// player can see and that receive light (see [`Board::lighting`]) and draw
+    /// everything else as unlit darkness. Sight and light are blocked by opaque cells.
     /// Loaded from / saved to the `dark` key in the map file's `[map]` header;
     /// defaults to `false` (fully lit).
     pub dark: bool,
@@ -275,48 +274,74 @@ impl Board {
         self.solid_at(x, y).is_none()
     }
 
-    /// Returns `true` if cell `(x, y)` blocks line of sight.
+    /// Returns `true` if cell `(x, y)` blocks line of sight (and light).
     ///
     /// A cell is sight-blocking if its grid terrain is opaque (e.g. a `Wall`)
-    /// **or** any object on it is opaque. This is the input to field-of-view on
-    /// [`dark`](Board::dark) boards; see [`Board::player_fov`].
+    /// **or** any object on it is opaque. This is the input to lighting on
+    /// [`dark`](Board::dark) boards; see [`Board::lighting`].
     /// Panics if `x` or `y` are out of bounds.
     pub fn is_opaque_at(&self, x: usize, y: usize) -> bool {
         self.get(x, y).1.behavior().opaque
             || self.objects.values().any(|o| o.x == x && o.y == y && o.opaque)
     }
 
-    /// Computes the player's field of view on this board.
+    /// Computes lighting + line-of-sight for the player on this board.
     ///
     /// Returns `None` unless the board is [`dark`](Board::dark) — a lit board
-    /// needs no FOV, and front-ends draw every cell. On a dark board it builds a
-    /// [`doryen_fov`] transparency map (opaque cells from [`is_opaque_at`](Board::is_opaque_at)
-    /// block sight), casts recursive shadow-casting from the player out to
-    /// [`SIGHT_RADIUS`](crate::fov::SIGHT_RADIUS), and returns the resulting
-    /// [`Visibility`] for the front-end to query per cell.
-    pub fn player_fov(&self) -> Option<Visibility> {
+    /// needs no lighting and front-ends draw every cell at full color. On a dark
+    /// board it (a) casts an unbounded line-of-sight field from the player, then
+    /// (b) accumulates colored light from every source — the player's torch
+    /// (radius `player_torch`, white), each object with `light > 0`, and each
+    /// terrain cell with [`Archetype::light`] `> 0` — each source colored by its
+    /// own glyph fg and falling off linearly to its radius. Opaque cells (via
+    /// [`is_opaque_at`](Board::is_opaque_at)) block both sight and light.
+    pub fn lighting(&self, player_torch: u32) -> Option<Lighting> {
         if !self.dark {
             return None;
         }
-        // Seed every cell's transparency; MapData defaults to all-transparent, so
-        // we only need to knock out the opaque ones — but set all to stay explicit.
-        let mut map = MapData::new(self.width, self.height);
-        for y in 0..self.height {
-            for x in 0..self.width {
-                map.set_transparent(x, y, !self.is_opaque_at(x, y));
+        let (w, h) = (self.width, self.height);
+        let mut lighting = Lighting::new(w, h);
+        // One caster whose transparency is seeded once from the opaque cells;
+        // reused for the LOS pass and every light source (its FOV is cleared per cast).
+        let mut caster = FovCaster::new(w, h, |x, y| !self.is_opaque_at(x, y));
+
+        let (px, py) = (self.player.x as usize, self.player.y as usize);
+        // (a) Player line of sight — unbounded (radius 0), pure geometry.
+        caster.cast(px, py, 0, |x, y| lighting.set_los(x, y));
+
+        // (b) Accumulate each light source into the per-cell color buffer. A
+        // source paints every cell it can see within its radius, tinted by its
+        // glyph fg and dimmed by a linear falloff (full at the source, 0 at the edge).
+        let mut add_source = |lighting: &mut Lighting, sx: usize, sy: usize, radius: u32, color: [f32; 3]| {
+            let r = radius as f32;
+            caster.cast(sx, sy, radius as usize, |x, y| {
+                let d = ((x as f32 - sx as f32).powi(2) + (y as f32 - sy as f32).powi(2)).sqrt();
+                let falloff = (1.0 - d / r).max(0.0);
+                lighting.add_light(x, y, [color[0] * falloff, color[1] * falloff, color[2] * falloff]);
+            });
+        };
+
+        // The player's torch: a white light centered on the player.
+        if player_torch > 0 {
+            add_source(&mut lighting, px, py, player_torch, [1.0, 1.0, 1.0]);
+        }
+        // Light-emitting objects: color = their own glyph foreground.
+        for o in self.objects.values() {
+            if o.light > 0 {
+                add_source(&mut lighting, o.x, o.y, o.light, color_to_rgb(o.glyph.fg));
             }
         }
-        // `light_walls = true` lights opaque cells at the edge of sight (the wall
-        // you're looking *at* is visible), rather than only the open cells before it.
-        let mut algo = FovRecursiveShadowCasting::new();
-        algo.compute_fov(
-            &mut map,
-            self.player.x as usize,
-            self.player.y as usize,
-            SIGHT_RADIUS,
-            true,
-        );
-        Some(Visibility::new(map))
+        // Glowing terrain (e.g. a `Torch` cell): color = the cell's glyph foreground.
+        for y in 0..h {
+            for x in 0..w {
+                let (glyph, arch) = self.get(x, y);
+                let radius = arch.light();
+                if radius > 0 {
+                    add_source(&mut lighting, x, y, radius, color_to_rgb(glyph.fg));
+                }
+            }
+        }
+        Some(lighting)
     }
 
     /// Whether the cell's single solid occupant (if any) can be pushed in `dir`.
@@ -1184,11 +1209,11 @@ pub(crate) mod tests {
     }
 
     #[test]
-    fn player_fov_none_when_not_dark() {
-        // A lit board needs no FOV; front-ends draw every cell.
+    fn lighting_none_when_not_dark() {
+        // A lit board needs no lighting; front-ends draw every cell.
         let board = open_board(5, 1, (0, 0), vec![]);
         assert!(!board.dark);
-        assert!(board.player_fov().is_none());
+        assert!(board.lighting(10).is_none());
     }
 
     #[test]
@@ -1202,17 +1227,50 @@ pub(crate) mod tests {
     #[test]
     fn dark_board_hides_cells_behind_a_wall() {
         // Player at the left end of a 1-wide corridor; a wall at x=2 occludes
-        // everything past it. Cells before the wall (and the wall itself) are
-        // visible; the cell behind the wall is not.
+        // everything past it. The player's torch lights cells before the wall
+        // (and the wall itself); the cells behind the wall are neither lit nor
+        // in line of sight, so they are not visible.
         let mut board = open_board(5, 1, (0, 0), vec![]);
         board.dark = true;
         wall_at(&mut board, 2, 0);
 
-        let vis = board.player_fov().expect("dark board yields a Visibility");
-        assert!(vis.is_visible(0, 0)); // the player's own cell
-        assert!(vis.is_visible(1, 0)); // open cell before the wall
-        assert!(vis.is_visible(2, 0)); // the wall itself (light_walls = true)
-        assert!(!vis.is_visible(3, 0)); // occluded behind the wall
-        assert!(!vis.is_visible(4, 0)); // occluded behind the wall
+        let lit = board.lighting(10).expect("dark board yields Lighting");
+        assert!(lit.is_visible(0, 0)); // the player's own cell
+        assert!(lit.is_visible(1, 0)); // open cell before the wall
+        assert!(lit.is_visible(2, 0)); // the wall itself (light_walls = true)
+        assert!(!lit.is_visible(3, 0)); // occluded behind the wall
+        assert!(!lit.is_visible(4, 0)); // occluded behind the wall
+    }
+
+    #[test]
+    fn unlit_cell_in_sight_is_not_visible() {
+        // A long lit-free corridor: with a tiny torch, far cells are in line of
+        // sight but receive no light, so they are not visible (LOS ∩ lit).
+        let mut board = open_board(10, 1, (0, 0), vec![]);
+        board.dark = true;
+        let lit = board.lighting(2).expect("dark board yields Lighting");
+        assert!(lit.is_visible(0, 0)); // at the torch
+        assert!(lit.is_visible(1, 0)); // within the torch radius
+        assert!(!lit.is_visible(8, 0)); // in sight but unlit → dark
+    }
+
+    #[test]
+    fn object_light_tints_toward_its_color() {
+        // A dark board with no player torch and one red-glyph light object: the
+        // object's cell is lit red, so a white base tints red (green/blue killed).
+        let mut board = open_board(3, 1, (1, 0), vec![]);
+        board.dark = true;
+        let mut lamp = ObjectDef::new(1, 0);
+        lamp.solid = false;
+        lamp.light = 4;
+        lamp.glyph = Glyph { tile: 1, fg: Rgba8 { r: 255, g: 0, b: 0, a: 255 }, bg: Rgba8 { r: 0, g: 0, b: 0, a: 255 } };
+        board.add_object(lamp);
+
+        let lit = board.lighting(0).expect("dark board yields Lighting"); // no player torch
+        let white = Rgba8 { r: 255, g: 255, b: 255, a: 255 };
+        let t = lit.tint(1, 0, white);
+        assert!(t.r > 0, "red channel survives");
+        assert_eq!(t.g, 0, "green killed by red light");
+        assert_eq!(t.b, 0, "blue killed by red light");
     }
 }
diff --git a/kiln-core/src/fov.rs b/kiln-core/src/fov.rs
index 6ba2114..c219eb0 100644
--- a/kiln-core/src/fov.rs
+++ b/kiln-core/src/fov.rs
@@ -1,41 +1,154 @@
-//! Field-of-view computation for "dark" boards.
+//! Lighting and field-of-view for "dark" boards.
 //!
-//! A [`Board`](crate::board::Board) marked `dark` only reveals cells the player
-//! can actually see; everything else is drawn as unlit darkness by the
-//! front-end. Visibility is computed with the [`doryen_fov`] crate's recursive
+//! A [`Board`](crate::board::Board) marked `dark` reveals a cell only when the
+//! player has a **line of sight** to it *and* it receives **light** from some
+//! source. Both are computed with the [`doryen_fov`] crate's recursive
 //! shadow-casting algorithm — pure Rust and WASM-safe, matching kiln's
 //! WASM-first requirement.
 //!
-//! [`Board::player_fov`](crate::board::Board::player_fov) builds a [`Visibility`]
-//! by marking each opaque cell as sight-blocking and casting from the player's
-//! position; the front-end then queries [`Visibility::is_visible`] per cell.
+//! [`Board::lighting`](crate::board::Board::lighting) builds a [`Lighting`] by:
+//! 1. casting an unbounded line-of-sight field from the player (pure geometry),
+//! 2. accumulating per-cell colored light from every source — the player's
+//!    torch plus each light-emitting object and glowing terrain cell — where a
+//!    source's color is its own glyph foreground and its contribution falls off
+//!    linearly to zero at its radius.
+//!
+//! The front-end then, per cell, asks [`Lighting::is_visible`] (LOS ∩ lit) and
+//! [`Lighting::tint`] (modulate the glyph's colors by the received light).
 
+use color::Rgba8;
 use doryen_fov::MapData;
 
-/// How far the player can see on a dark board, in cells.
+/// Default player torch radius in cells, used when a world omits `torch = N`
+/// from its `[world]` header. See [`World::torch`](crate::world::World::torch).
 pub const SIGHT_RADIUS: usize = 10;
 
-/// The result of a field-of-view computation: which board cells are currently
-/// visible to the player. Produced by
-/// [`Board::player_fov`](crate::board::Board::player_fov) and queried per cell
-/// by front-ends when rendering a dark board.
-pub struct Visibility {
-    /// The `doryen_fov` map holding per-cell transparency + computed visibility.
+/// A finished lighting computation for one dark-board frame: per-cell player
+/// line-of-sight plus accumulated colored light. Produced by
+/// [`Board::lighting`](crate::board::Board::lighting); queried per cell by
+/// front-ends when rendering a dark board.
+pub struct Lighting {
+    /// Board width in cells (row stride for `los` / `light`).
+    width: usize,
+    /// Player line-of-sight: `true` where the player has an unobstructed
+    /// sightline, regardless of whether the cell is lit.
+    los: Vec<bool>,
+    /// Accumulated linear light per cell as `[r, g, b]` in `0.0..` (may exceed
+    /// `1.0` where lights overlap; clamped when applied). Zero means unlit.
+    light: Vec<[f32; 3]>,
+}
+
+impl Lighting {
+    /// Builds an all-dark lighting buffer of `width * height` cells for the
+    /// caller ([`Board::lighting`]) to fill.
+    pub(crate) fn new(width: usize, height: usize) -> Self {
+        Self {
+            width,
+            los: vec![false; width * height],
+            light: vec![[0.0; 3]; width * height],
+        }
+    }
+
+    /// Is board cell `(x, y)` visible — player has a sightline **and** it is lit?
+    ///
+    /// This is the render/​speech gate: a lit area the player can't line up to
+    /// (around a corner) is not visible, and a cell in view but unlit is dark.
+    pub fn is_visible(&self, x: usize, y: usize) -> bool {
+        let i = y * self.width + x;
+        self.los[i] && intensity(self.light[i]) > LIGHT_EPSILON
+    }
+
+    /// Modulates a base color by the light this cell receives: each channel is
+    /// multiplied by the accumulated light (clamped to `1.0`), so a white light
+    /// just dims with distance while a colored light tints toward its own hue.
+    /// Alpha is preserved. Callers should only tint cells that
+    /// [`is_visible`](Lighting::is_visible).
+    pub fn tint(&self, x: usize, y: usize, base: Rgba8) -> Rgba8 {
+        let l = self.light[y * self.width + x];
+        Rgba8 {
+            r: (base.r as f32 * l[0].min(1.0)) as u8,
+            g: (base.g as f32 * l[1].min(1.0)) as u8,
+            b: (base.b as f32 * l[2].min(1.0)) as u8,
+            a: base.a,
+        }
+    }
+
+    /// Marks cell `(x, y)` as within the player's line of sight. Used by the
+    /// LOS pass in [`Board::lighting`].
+    pub(crate) fn set_los(&mut self, x: usize, y: usize) {
+        self.los[y * self.width + x] = true;
+    }
+
+    /// Adds `amount` linear light (already color- and falloff-scaled) to cell
+    /// `(x, y)`. Used by the per-source accumulation in [`Board::lighting`].
+    pub(crate) fn add_light(&mut self, x: usize, y: usize, amount: [f32; 3]) {
+        let cell = &mut self.light[y * self.width + x];
+        cell[0] += amount[0];
+        cell[1] += amount[1];
+        cell[2] += amount[2];
+    }
+}
+
+/// Cells dimmer than this (summed linear intensity) count as unlit.
+const LIGHT_EPSILON: f32 = 0.001;
+
+/// Summed linear intensity of an accumulated light value — the "is it lit at
+/// all" measure used by [`Lighting::is_visible`].
+fn intensity(l: [f32; 3]) -> f32 {
+    l[0] + l[1] + l[2]
+}
+
+/// Normalizes an 8-bit color to a `0.0..=1.0` linear-ish RGB triple, used as a
+/// light source's color (a source emits its own glyph's foreground color).
+pub(crate) fn color_to_rgb(c: Rgba8) -> [f32; 3] {
+    [c.r as f32 / 255.0, c.g as f32 / 255.0, c.b as f32 / 255.0]
+}
+
+/// A reusable helper wrapping the `doryen_fov` shadow-caster and a single
+/// scratch [`MapData`] whose transparency is set once from the board's opaque
+/// cells, so [`Board::lighting`] can cast many sources without reallocating.
+pub(crate) struct FovCaster {
+    algo: doryen_fov::FovRecursiveShadowCasting,
     map: MapData,
 }
 
-impl Visibility {
-    /// Wraps a finished [`MapData`] (visibility already computed) as a
-    /// [`Visibility`]. Called by [`Board::player_fov`](crate::board::Board::player_fov).
-    pub(crate) fn new(map: MapData) -> Self {
-        Self { map }
+impl FovCaster {
+    /// Builds a caster over a `width * height` map. `transparent(x, y)` supplies
+    /// each cell's transparency (`true` = light/sight passes through).
+    pub(crate) fn new(width: usize, height: usize, transparent: impl Fn(usize, usize) -> bool) -> Self {
+        let mut map = MapData::new(width, height);
+        for y in 0..height {
+            for x in 0..width {
+                map.set_transparent(x, y, transparent(x, y));
+            }
+        }
+        Self {
+            algo: doryen_fov::FovRecursiveShadowCasting::new(),
+            map,
+        }
     }
 
-    /// Is board cell `(x, y)` currently visible to the player?
-    ///
-    /// Out-of-bounds coordinates are not expected (the caller iterates the
-    /// board grid) and would panic inside [`MapData::is_in_fov`].
-    pub fn is_visible(&self, x: usize, y: usize) -> bool {
-        self.map.is_in_fov(x, y)
+    /// Casts a field of view from `(x, y)` out to `radius` (0 = unbounded) and
+    /// invokes `visit(cx, cy)` for every cell it lights. `light_walls = true`
+    /// includes opaque cells at the edge of the field. Clears prior results
+    /// first, so successive calls are independent.
+    pub(crate) fn cast(
+        &mut self,
+        x: usize,
+        y: usize,
+        radius: usize,
+        mut visit: impl FnMut(usize, usize),
+    ) {
+        use doryen_fov::FovAlgorithm;
+        self.map.clear_fov();
+        self.algo.compute_fov(&mut self.map, x, y, radius, true);
+        let (w, h) = (self.map.width, self.map.height);
+        for cy in 0..h {
+            for cx in 0..w {
+                if self.map.is_in_fov(cx, cy) {
+                    visit(cx, cy);
+                }
+            }
+        }
     }
 }
diff --git a/kiln-core/src/game.rs b/kiln-core/src/game.rs
index 5286baf..64fa0f6 100644
--- a/kiln-core/src/game.rs
+++ b/kiln-core/src/game.rs
@@ -161,6 +161,7 @@ impl GameState {
         let world = World {
             name: String::new(),
             start: "board".to_string(),
+            torch: crate::fov::SIGHT_RADIUS as u32,
             scripts,
             boards: std::collections::HashMap::from([("board".to_string(), board_ref)]),
         };
@@ -182,6 +183,12 @@ impl GameState {
         &self.current_board_name
     }
 
+    /// The player's torch radius (world-wide config; see [`World::torch`]),
+    /// passed to [`Board::lighting`] when rendering a dark board.
+    pub fn torch(&self) -> u32 {
+        self.world.torch
+    }
+
     /// Returns a clone of the `Rc` for the active board.
     ///
     /// Lets a front-end hold a reference to the current board across a board
@@ -304,6 +311,11 @@ impl GameState {
                             obj.glyph.tile = tile;
                         }
                     }
+                    Action::SetLight(radius) => {
+                        if let Some(obj) = board.objects.get_mut(&ba.source) {
+                            obj.light = radius;
+                        }
+                    }
                     Action::SetTag {
                         target,
                         tag,
diff --git a/kiln-core/src/layer.rs b/kiln-core/src/layer.rs
index 22790d6..abb3747 100644
--- a/kiln-core/src/layer.rs
+++ b/kiln-core/src/layer.rs
@@ -85,6 +85,10 @@ pub(crate) struct PaletteEntry {
     /// Object pushability (defaults `false`). Only for `kind = "object"`.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub pushable: Option<bool>,
+    /// Light radius in cells emitted on a dark board (defaults `0` = none).
+    /// Only for `kind = "object"`. See [`ObjectDef::light`].
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub light: Option<u32>,
     /// Rhai script name. Only for `kind = "object"`.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub script_name: Option<String>,
@@ -126,6 +130,8 @@ pub(crate) struct ObjectTemplate {
     pub solid: bool,
     pub opaque: bool,
     pub pushable: bool,
+    /// Light radius in cells (0 = none); see [`ObjectDef::light`].
+    pub light: u32,
     pub script_name: Option<String>,
     pub tags: Vec<String>,
     pub name: Option<String>,
@@ -174,6 +180,7 @@ fn resolve_entry(ch: char, e: &PaletteEntry, errors: &mut Vec<LogLine>) -> Resol
             solid: e.solid.unwrap_or(true),
             opaque: e.opaque.unwrap_or(true),
             pushable: e.pushable.unwrap_or(false),
+            light: e.light.unwrap_or(0),
             script_name: e.script_name.clone(),
             tags: e.tags.clone().unwrap_or_default(),
             name: e.name.clone(),
diff --git a/kiln-core/src/lib.rs b/kiln-core/src/lib.rs
index 3719edb..4779470 100644
--- a/kiln-core/src/lib.rs
+++ b/kiln-core/src/lib.rs
@@ -8,7 +8,7 @@ pub mod colors;
 pub mod cp437;
 /// Procedural floor generators ([`floor::FloorGenerator`]).
 pub mod floor;
-/// Field-of-view computation for dark boards ([`fov::Visibility`]).
+/// Lighting & field-of-view for dark boards ([`fov::Lighting`]).
 pub mod fov;
 /// Core game types: [`board::Board`], [`glyph::Glyph`], [`archetype::Archetype`], etc.
 pub mod game;
@@ -28,7 +28,7 @@ pub mod player;
 pub mod keys;
 pub use archetype::{Archetype, Builtin};
 pub use board::Board;
-pub use fov::{SIGHT_RADIUS, Visibility};
+pub use fov::{Lighting, SIGHT_RADIUS};
 pub use utils::Direction;
 
 #[cfg(test)]
diff --git a/kiln-core/src/map_file.rs b/kiln-core/src/map_file.rs
index f539ef1..2119885 100644
--- a/kiln-core/src/map_file.rs
+++ b/kiln-core/src/map_file.rs
@@ -319,6 +319,7 @@ impl TryFrom<MapFile> for Board {
                     solid: t.solid,
                     opaque: t.opaque,
                     pushable: t.pushable,
+                    light: t.light,
                     // Hand-placed objects are never grab targets; only expanded
                     // grab archetypes (e.g. gems) set this (see expand_builtin_archetypes).
                     grab: false,
@@ -357,6 +358,7 @@ impl TryFrom<MapFile> for Board {
                     solid: false,
                     opaque: false,
                     pushable: false,
+                    light: 0,
                     grab: false,
                     script_name: Some(t.script_name),
                     builtin_script: None,
@@ -564,6 +566,7 @@ fn grid_to_data(board: &Board) -> GridData {
                 solid: Some(o.solid),
                 opaque: Some(o.opaque),
                 pushable: Some(o.pushable),
+                light: (o.light > 0).then_some(o.light),
                 script_name: o.script_name.clone(),
                 tags: (!tags.is_empty()).then_some(tags),
                 name: o.name.clone(),
diff --git a/kiln-core/src/object_def.rs b/kiln-core/src/object_def.rs
index f6b1795..243a2b1 100644
--- a/kiln-core/src/object_def.rs
+++ b/kiln-core/src/object_def.rs
@@ -51,6 +51,11 @@ pub struct ObjectDef {
     /// remove itself via `die()`). Set when a grab archetype (e.g. a gem) is
     /// expanded into an object. Defaults to `false`.
     pub grab: bool,
+    /// Light radius in cells that this object emits on a `dark` board (0 = no
+    /// light). The emitted *color* is this object's own glyph foreground color,
+    /// so a red glyph casts red light. See [`crate::fov`] for the lighting model.
+    /// Scripts can change it at runtime via `set_light(n)`. Defaults to `0`.
+    pub light: u32,
     /// Compile-key of the Rhai script that drives this object: a name in
     /// [`World::scripts`](crate::world::World::scripts) for a hand-authored object,
     /// or a synthetic `BUILTIN_*` name set when a script-backed archetype is
@@ -102,6 +107,7 @@ impl ObjectDef {
             opaque: true,
             pushable: false,
             grab: false,
+            light: 0,
             script_name: None,
             builtin_script: None,
             tags: HashSet::new(),
diff --git a/kiln-core/src/script.rs b/kiln-core/src/script.rs
index c3ad3ce..0070cce 100644
--- a/kiln-core/src/script.rs
+++ b/kiln-core/src/script.rs
@@ -418,6 +418,13 @@ fn register_write_api(engine: &mut Engine, board: BoardRef, log_sink: LogSink) {
         emit(&b, source_of(&ctx), Action::SetTile(tile as u32));
     });
 
+    // set_light(radius): change the source object's emitted light radius in cells
+    // (0 = no light). Negatives clamp to 0. Only visible on `dark` boards.
+    let b = board.clone();
+    engine.register_fn("set_light", move |ctx: NativeCallContext, radius: i64| {
+        emit(&b, source_of(&ctx), Action::SetLight(radius.max(0) as u32));
+    });
+
     // alter_gems(n): change the player's gem count (negative subtracts; clamped at 0).
     let b = board.clone();
     engine.register_fn("alter_gems", move |ctx: NativeCallContext, n: i64| {
diff --git a/kiln-core/src/tests/game_portals.rs b/kiln-core/src/tests/game_portals.rs
index d13703d..0e52959 100644
--- a/kiln-core/src/tests/game_portals.rs
+++ b/kiln-core/src/tests/game_portals.rs
@@ -59,6 +59,7 @@ fn two_board_world() -> World {
     World {
         name: "test".into(),
         start: "b1".into(),
+        torch: 10,
         scripts: HashMap::new(),
         boards: HashMap::from([
             ("b1".to_string(), Rc::new(RefCell::new(b1))),
diff --git a/kiln-core/src/world.rs b/kiln-core/src/world.rs
index 5da572c..d9d0f57 100644
--- a/kiln-core/src/world.rs
+++ b/kiln-core/src/world.rs
@@ -1,6 +1,7 @@
 //! World type: a named collection of boards loaded from a single `.toml` file.
 
 use crate::board::Board;
+use crate::fov::SIGHT_RADIUS;
 use crate::map_file::MapFile;
 use serde::Deserialize;
 use std::cell::RefCell;
@@ -22,6 +23,11 @@ pub struct World {
     pub name: String,
     /// Key of the starting board; matches a key in [`World::boards`].
     pub start: String,
+    /// The player's torch radius in cells on `dark` boards — world-wide config
+    /// from the `[world]` header (`torch = N`), defaulting to [`SIGHT_RADIUS`]
+    /// when absent. The player's torch is a white light source centered on the
+    /// player; see [`Board::lighting`](crate::board::Board::lighting).
+    pub torch: u32,
     /// Named Rhai scripts shared across all boards: script name → source text.
     ///
     /// Objects on any board reference a script by name via
@@ -49,6 +55,7 @@ impl World {
         World {
             name: self.name.clone(),
             start: self.start.clone(),
+            torch: self.torch,
             scripts: self.scripts.clone(),
             boards: self
                 .boards
@@ -78,6 +85,9 @@ struct WorldHeader {
     name: String,
     /// Key of the board to start on; must match a key in `[boards]`.
     start: String,
+    /// Optional player torch radius on dark boards; defaults to [`SIGHT_RADIUS`].
+    #[serde(default)]
+    torch: Option<u32>,
 }
 
 /// Load a world from a `.toml` world file at `path`.
@@ -110,6 +120,7 @@ pub fn load(path: &str) -> Result<World, Box<dyn std::error::Error>> {
     Ok(World {
         name: wf.world.name,
         start: wf.world.start,
+        torch: wf.world.torch.unwrap_or(SIGHT_RADIUS as u32),
         scripts: wf.scripts,
         boards,
     })
@@ -134,6 +145,7 @@ mod tests {
         let world = World {
             name: "w".into(),
             start: "start".into(),
+            torch: 10,
             scripts: HashMap::new(),
             boards,
         };
diff --git a/kiln-tui/src/main.rs b/kiln-tui/src/main.rs
index 4bfea88..3a6ef5b 100644
--- a/kiln-tui/src/main.rs
+++ b/kiln-tui/src/main.rs
@@ -424,10 +424,10 @@ fn draw_board_area(frame: &mut Frame, inner: Rect, game: &GameState, ui: &mut Ui
         );
     } else {
         let board = &game.board();
-        // On a dark board this is the player's field of view; on a lit board it's
-        // None (draw everything). Computed once and shared by both widgets so the
-        // board and its speech bubbles agree on what's visible.
-        let fov = board.player_fov();
+        // On a dark board this is the player's lighting (LOS + colored light); on a
+        // lit board it's None (draw everything). Computed once and shared by both
+        // widgets so the board and its speech bubbles agree on what's visible.
+        let fov = board.lighting(game.torch());
         frame.render_widget(BoardWidget::new(board).fov(fov.as_ref()), inner);
         frame.render_widget(
             SpeechBubblesWidget::new(board, &game.speech_bubbles).fov(fov.as_ref()),
diff --git a/kiln-tui/src/render.rs b/kiln-tui/src/render.rs
index 687cc43..798deac 100644
--- a/kiln-tui/src/render.rs
+++ b/kiln-tui/src/render.rs
@@ -8,7 +8,7 @@
 use crate::utils::rgba8_to_color;
 use color::Rgba8;
 use kiln_core::Board;
-use kiln_core::Visibility;
+use kiln_core::Lighting;
 use kiln_core::cp437::tile_to_char;
 use ratatui::buffer::Buffer;
 use ratatui::layout::Rect;
@@ -27,10 +27,10 @@ pub struct BoardWidget<'a> {
     /// The board cell (x, y) the viewport scrolls to keep visible. Defaults to
     /// the player position so play mode requires no extra setup.
     focus: (i32, i32),
-    /// The player's field of view on a [`dark`](Board::dark) board, if any. When
-    /// `Some`, cells not in view are drawn as darkness instead of their glyph.
-    /// `None` (a lit board) draws every cell normally.
-    fov: Option<&'a Visibility>,
+    /// The player's lighting on a [`dark`](Board::dark) board, if any. When
+    /// `Some`, cells that aren't visible are drawn as darkness and visible cells
+    /// are tinted by the light they receive. `None` (a lit board) draws normally.
+    fov: Option<&'a Lighting>,
 }
 
 impl<'a> BoardWidget<'a> {
@@ -47,9 +47,10 @@ impl<'a> BoardWidget<'a> {
         self
     }
 
-    /// Supplies the player's field of view (see [`Board::player_fov`]). When
-    /// `Some`, cells outside it render as darkness; `None` renders everything.
-    pub fn fov(mut self, fov: Option<&'a Visibility>) -> Self {
+    /// Supplies the player's lighting (see [`Board::lighting`]). When `Some`,
+    /// cells outside view render as darkness and visible cells are tinted by
+    /// their received light; `None` renders everything at full color.
+    pub fn fov(mut self, fov: Option<&'a Lighting>) -> Self {
         self.fov = fov;
         self
     }
@@ -147,16 +148,22 @@ impl Widget for BoardWidget<'_> {
                 let bx = off_x + col;
                 let sx = area.x + pad_x + col as u16;
 
-                // On a dark board, a cell outside the player's field of view is
-                // drawn as darkness (blank cell, dark-gray background) instead of
-                // its real glyph. A lit board (`fov == None`) shows every cell.
-                let visible = self.fov.is_none_or(|v| v.is_visible(bx, by));
+                // On a dark board, a cell the player can't see (no sightline or
+                // unlit) is drawn as darkness (blank on dark gray). A visible cell
+                // is drawn with its glyph, tinted by the light it receives. A lit
+                // board (`fov == None`) shows every cell at full color.
+                let visible = self.fov.is_none_or(|l| l.is_visible(bx, by));
                 if let Some(cell) = buf.cell_mut((sx, sy)) {
                     if visible {
                         let glyph = board.glyph_at(bx, by);
+                        // Modulate by lighting when the board is dark; pass through otherwise.
+                        let (fg, bg) = match self.fov {
+                            Some(l) => (l.tint(bx, by, glyph.fg), l.tint(bx, by, glyph.bg)),
+                            None => (glyph.fg, glyph.bg),
+                        };
                         cell.set_char(tile_to_char(glyph.tile))
-                            .set_fg(rgba8_to_color(glyph.fg))
-                            .set_bg(rgba8_to_color(glyph.bg));
+                            .set_fg(rgba8_to_color(fg))
+                            .set_bg(rgba8_to_color(bg));
                     } else {
                         cell.set_char(' ')
                             .set_fg(rgba8_to_color(DARKNESS_BG))
@@ -176,6 +183,7 @@ mod tests {
     use kiln_core::map_file::MapFile;
     use ratatui::buffer::Buffer;
     use ratatui::layout::Rect;
+    use ratatui::style::Color;
     use ratatui::widgets::Widget;
 
     /// Builds a tiny dark board: a 5×1 corridor with the player at the left end
@@ -200,8 +208,8 @@ mod tests {
     #[test]
     fn dark_board_renders_occluded_cells_as_darkness() {
         let board = dark_corridor();
-        let fov = board.player_fov();
-        assert!(fov.is_some(), "a dark board must produce a field of view");
+        let fov = board.lighting(10);
+        assert!(fov.is_some(), "a dark board must produce lighting");
 
         let area = Rect::new(0, 0, 5, 1);
         let mut buf = Buffer::empty(area);
@@ -220,10 +228,10 @@ mod tests {
 
     #[test]
     fn lit_board_renders_every_cell_normally() {
-        // The same board without `dark` gets no FOV, so nothing is hidden.
+        // The same board without `dark` gets no lighting, so nothing is hidden.
         let mut board = dark_corridor();
         board.dark = false;
-        assert!(board.player_fov().is_none());
+        assert!(board.lighting(10).is_none());
 
         let area = Rect::new(0, 0, 5, 1);
         let mut buf = Buffer::empty(area);
@@ -232,6 +240,36 @@ mod tests {
         assert_ne!(buf[(4, 0)].bg, rgba8_to_color(DARKNESS_BG));
     }
 
+    #[test]
+    fn colored_object_light_tints_nearby_and_darkens_far() {
+        // A dark 6×1 corridor, no player torch: a single red light object at x=2
+        // (radius 2) tints its own cell red; a cell beyond its reach is darkness.
+        let toml = r##"
+            [map]
+            name = "lit"
+            width = 6
+            height = 1
+            dark = true
+            [grid]
+            sparse = [ { x = 2, y = 0, ch = "L" } ]
+            [grid.palette]
+            "L" = { kind = "object", tile = 1, fg = "#ff0000", bg = "#000000", solid = false, light = 2 }
+        "##;
+        let board = Board::try_from(toml::from_str::<MapFile>(toml).unwrap()).unwrap();
+        let fov = board.lighting(0); // no player torch — only the object lights
+
+        let area = Rect::new(0, 0, 6, 1);
+        let mut buf = Buffer::empty(area);
+        BoardWidget::new(&board).fov(fov.as_ref()).render(area, &mut buf);
+
+        // The light's own cell is visible and tinted red (green/blue killed).
+        let lit = buf[(2, 0)].fg;
+        assert!(matches!(lit, Color::Rgb(r, 0, 0) if r > 0), "light cell tinted red, got {lit:?}");
+        // x=5 is out of the light's radius → darkness.
+        assert_eq!(buf[(5, 0)].symbol(), " ");
+        assert_eq!(buf[(5, 0)].bg, rgba8_to_color(DARKNESS_BG));
+    }
+
     #[test]
     fn axis_centers_a_small_board() {
         // 10-cell board in a 20-cell view: no scroll, 5 cells of pad each side.
diff --git a/kiln-tui/src/speech.rs b/kiln-tui/src/speech.rs
index 47c822e..76c213a 100644
--- a/kiln-tui/src/speech.rs
+++ b/kiln-tui/src/speech.rs
@@ -1,7 +1,7 @@
 use crate::render::BoardWidget;
 use crate::utils::rects_overlap;
 use kiln_core::game::SpeechBubble;
-use kiln_core::{Board, Direction, Visibility};
+use kiln_core::{Board, Direction, Lighting};
 use ratatui::buffer::Buffer;
 use ratatui::layout::Rect;
 use ratatui::prelude::{Color, Line, Style, Widget};
@@ -19,10 +19,10 @@ pub struct SpeechBubblesWidget<'a> {
     pub board: &'a Board,
     /// The active speech bubbles to render.
     pub bubbles: &'a [SpeechBubble],
-    /// The player's field of view on a dark board, if any. A speaker outside it
-    /// still gets a bubble, but with no tail (like an off-screen speaker) —
+    /// The player's lighting on a dark board, if any. A speaker the player can't
+    /// see still gets a bubble, but with no tail (like an off-screen speaker) —
     /// you hear the unseen thing without a line pointing to where it hides.
-    fov: Option<&'a Visibility>,
+    fov: Option<&'a Lighting>,
 }
 
 /// A fully-resolved bubble placement ready for the three draw passes.
@@ -47,9 +47,9 @@ impl<'a> SpeechBubblesWidget<'a> {
         Self { board, bubbles, fov: None }
     }
 
-    /// Supplies the player's field of view (see [`Board::player_fov`]). A speaker
-    /// outside it has its tail suppressed; `None` (a lit board) leaves tails as-is.
-    pub fn fov(mut self, fov: Option<&'a Visibility>) -> Self {
+    /// Supplies the player's lighting (see [`Board::lighting`]). A speaker the
+    /// player can't see has its tail suppressed; `None` (a lit board) leaves tails as-is.
+    pub fn fov(mut self, fov: Option<&'a Lighting>) -> Self {
         self.fov = fov;
         self
     }
diff --git a/maps/dark.toml b/maps/dark.toml
index 7c38925..3748593 100644
--- a/maps/dark.toml
+++ b/maps/dark.toml
@@ -1,6 +1,9 @@
 [world]
 name = "Dark Maze"
 start = "cave"
+# The player's own torch is small, so external lights clearly matter. Remove this
+# line to fall back to the default radius of 10.
+torch = 4
 
 [scripts]
 # An always-talking object. Placed behind a wall so it starts out of the player's
@@ -31,9 +34,10 @@ height = 15
 dark = true
 floor = { generator = "stone" }
 
-# A room the player stands in, with a wall dividing it. The 'H' object sits in
-# the far chamber behind the wall (out of sight until you walk around); the 'L'
-# lantern sits in the open with the player.
+# The 'H' object glows magenta inside a walled chamber: its light fills that room
+# but the player can't see in until they line up with the gap in the wall. 'L' is
+# an amber lantern out in the open, and 'T' is a wall torch (glowing terrain) off
+# in a far corner — a warm point of light you'll only reach by walking to it.
 [boards.cave.grid]
 content = """
 ########################################
@@ -46,7 +50,7 @@ content = """
 #           #### ######                #
 #                                      #
 #                                      #
-#                                      #
+#                                 T    #
 #                                      #
 #                                      #
 #                                      #
@@ -55,5 +59,6 @@ content = """
 [boards.cave.grid.palette]
 "#" = { kind = "wall", tile = "#", fg = "#808080", bg = "#404040" }
 "@" = { kind = "player" }
-"H" = { kind = "object", tile = 2, fg = "#cc66cc", bg = "#000000", solid = true, name = "hidden", script_name = "hidden" }
-"L" = { kind = "object", tile = 15, fg = "#ffdd88", bg = "#000000", solid = true, name = "lantern", script_name = "lantern" }
+"T" = { kind = "torch" }  # glowing terrain: emits its own warm light
+"H" = { kind = "object", tile = 2, fg = "#cc66cc", bg = "#000000", solid = true, light = 5, name = "hidden", script_name = "hidden" }
+"L" = { kind = "object", tile = 15, fg = "#ffcc55", bg = "#000000", solid = true, light = 6, name = "lantern", script_name = "lantern" }