feat: trigger system for scripted events added.

5 files changed, 579 insertions, 2 deletions

diff --git a/building_guide/conditions.md b/building_guide/conditions.md
index ea17ed6..d58b35c 100644
--- a/building_guide/conditions.md
+++ b/building_guide/conditions.md
@@ -1,6 +1,7 @@
 ## Conditions Reference
 
-Conditions are used in talk options, exit gates, on-enter scripts, and use_interactions checks.
+Conditions are used in talk options, exit gates, on-enter scripts, use_interactions
+checks, room descriptions, object descriptions, and trigger value matching.
 
 ### Simple conditions
 
diff --git a/building_guide/rooms.md b/building_guide/rooms.md
index 7028393..5a414a3 100644
--- a/building_guide/rooms.md
+++ b/building_guide/rooms.md
@@ -208,5 +208,27 @@ mobs:
 - Hazards stack with mobs: an aggressive mob in a hazardous room hits you while the room
   hazard also rolls against you.
 
+### Room triggers — scripted events when flags change
+
+A room can carry a `triggers:` block. Each trigger watches a player or world flag
+and fires a sequence of timed steps when that flag's value changes. See `triggers.md`
+for the full reference.
+
+```yaml
+triggers:
+  - on_player_flag: 1001_look_sign
+    steps:
+      - delay: 5
+        message: "The cabin shakes as the small craft touches down"
+      - delay: 5
+        message: "The pistons hiss as the rear staircase opens"
+      - set_player_flags:
+          1001_touchdown: true
+```
+
+Room triggers are scoped to the room — broadcasts go to that room, mobs spawn there,
+and the trigger only fires when the flag-setting player is in that room. For
+server-wide events, use global triggers in `data/triggers/` instead.
+
 ---
 
diff --git a/building_guide/state.md b/building_guide/state.md
index 013e62a..2e0b5cc 100644
--- a/building_guide/state.md
+++ b/building_guide/state.md
@@ -4,5 +4,10 @@
 
 **Player flags** (`set_player_flags`, checked with `player_flag`) are per-character. Quest progress, "has read the sign," "paid the toll" — these are different for each player. Saved to the character YAML and persist across logins.
 
----
+### Triggers — flag-change events
+
+Any flag change (world or player) can activate a **trigger** — a timed sequence of
+messages, broadcasts, spawns, and further flag mutations. See `triggers.md` for
+the full system. This is how you turn "player looked at the sign" into "spaceship
+landed and stairs opened."
 
diff --git a/building_guide/tips.md b/building_guide/tips.md
index 307ea1e..b4abeb9 100644
--- a/building_guide/tips.md
+++ b/building_guide/tips.md
@@ -19,3 +19,5 @@
 9. **Shared depletion vs per-drop depletion.** Use `deplete_timer` for trees — the timer counts down while being chopped and regens when left alone. Use `depletes: true` on individual drops for rocks — they deplete on first successful gather.
 
 10. **Mob wander config goes in the room YAML**, not the mob definition. This lets the same `man` wander differently in different rooms.
+
+11. **Use triggers to decouple cause and effect.** Objects set flags; triggers watch flags. This way the same "pull lever" action can spawn a boss in one room, open a door in another, and broadcast to the server — all by watching the same flag from different triggers. Room triggers keep local events local; global triggers (`data/triggers/`) handle server-wide events.
diff --git a/building_guide/triggers.md b/building_guide/triggers.md
new file mode 100644
index 0000000..fa97e3a
--- /dev/null
+++ b/building_guide/triggers.md
@@ -0,0 +1,547 @@
+## Triggers
+
+Triggers let you script a sequence of timed events that fire when a flag changes
+value. They come in two flavors:
+
+- **Room triggers** — defined in room YAML under a `triggers:` block. The room is
+  the action context (broadcasts go to that room, mobs spawn there).
+- **Global triggers** — defined in `data/triggers/<id>.yaml`. These fire regardless
+  of where the flag-setting player is, and can broadcast to all online players.
+
+A trigger watches one flag (`on_player_flag` or `on_flag`). When that flag's value
+actually changes (from unset/falsy to a truthy/new value), the trigger's steps
+begin executing. Setting a flag to the same value it already has does **not** re-fire
+the trigger.
+
+### Quick Start: Landing Sequence
+
+A player looks at a sign, setting `1001_look_sign: true`. A room trigger in the
+same room watches that flag and plays a landing sequence:
+
+```yaml
+# data/rooms/intro/1001.yaml
+triggers:
+  - on_player_flag: 1001_look_sign
+    steps:
+      - delay: 5
+        message: "The cabin shakes as the small craft touches down"
+      - delay: 5
+        message: "The pistons hiss as the rear staircase opens"
+      - set_player_flags:
+          1001_touchdown: true
+```
+
+The sign object itself is unchanged — its `on_look` simply sets the flag. The trigger
+and the object are cleanly separated:
+
+```yaml
+# data/objects/unique/1001_sign.yaml
+on_look:
+  set_player_flags:
+    1001_look_sign: true
+```
+
+This separation is deliberate. The object sets flags. The trigger watches flags.
+Any system that sets a player flag (`on_look`, talk nodes, on-enter steps, exits,
+use interactions) can activate a trigger watching that flag.
+
+---
+
+### Step Actions
+
+Each step in a trigger's `steps:` list can carry a `delay` (ticks to wait) and
+one or more actions. All actions on a step fire simultaneously when the delay
+elapses.
+
+| Field              | Scope  | Description                                                                                           |
+| ------------------ | ------ | ----------------------------------------------------------------------------------------------------- |
+| `delay`            | both   | Ticks to wait before this step fires. `0` or omitted = fire on the reach tick.                        |
+| `message`          | player | Text sent to the triggering player only. Supports `%p` (player name) and `%v` (flag value) templates. |
+| `broadcast`        | room   | Text sent to everyone in the room. Inline color tags work; `\n` prefix is added automatically.        |
+| `broadcast_global` | world  | Text sent to every online player. Useful for server-wide announcements.                               |
+| `set_flags`        | world  | Mutates world flags (shared by all players).                                                          |
+| `set_player_flags` | player | Mutates player flags (per-character). Only valid for `on_player_flag` triggers.                       |
+| `spawn_mob`        | room   | Spawns a **transient** mob from a mob definition. See Transient Mobs below.                           |
+| `despawn_mob`      | room   | Removes all trigger-spawned mobs matching the given mob ID (and optionally owner).                    |
+| `give_item`        | player | Gives an item to the player's inventory.                                                              |
+| `take_item`        | player | Removes an item from the player's inventory.                                                          |
+| `teleport`         | player | Moves the player to a room ID.                                                                        |
+| `heal`             | player | Restores hitpoints.                                                                                   |
+
+---
+
+### Room-Level Triggers
+
+Room triggers go in the room YAML under a `triggers:` list. The room is
+automatically the context for broadcasts and mob spawns.
+
+#### Example 1: Boss arena — puzzle unlocks a boss
+
+Player activates an altar (sets a player flag), triggering a boss spawn:
+
+```yaml
+# data/rooms/dungeon/boss_chamber.yaml
+triggers:
+  - on_player_flag: activated_altar
+    steps:
+      - broadcast: "The altar glows with an eerie light..."
+      - delay: 10
+        broadcast: "The ground trembles beneath your feet."
+      - delay: 20
+        broadcast: "A massive guardian emerges from the shadows!"
+      - spawn_mob:
+          id: altar_guardian
+          owner_only: true
+          despawn_on_leave: true
+          despawn_rooms: [450, 451, 452]
+```
+
+The boss is `owner_only` — only the player who triggered it can interact with it.
+It won't despawn as long as the owner stays in rooms 450, 451, or 452 (a 3-room
+boss arena). When the owner leaves those rooms, the boss begins despawning.
+
+#### Example 2: Story beat — timed cutscene after NPC conversation
+
+An NPC conversation node sets `quest_ritual: started`. A room trigger plays a
+dramatic sequence for that player:
+
+```yaml
+triggers:
+  - on_player_flag: quest_ritual
+    steps:
+      - delay: 8
+        message: "The elder begins to chant in a language you don't recognize."
+      - delay: 6
+        message: "Wisps of light swirl around the altar."
+      - delay: 4
+        message: "The ground beneath you shudders as the ritual reaches its peak."
+      - delay: 6
+        broadcast: "A blinding flash fills the chamber!"
+      - teleport: 601
+        message: "You open your eyes. You're somewhere else entirely."
+```
+
+The final step uses both `broadcast` (everyone in the ritual room sees the flash)
+and `teleport` + `message` (the triggering player is moved and sees a personal
+message).
+
+#### Example 3: World-flag room trigger — shared environmental event
+
+A player pulls a lever (sets world flag `floodgate_open`). The room trigger
+broadcasts to everyone in the dam control room:
+
+```yaml
+# data/rooms/wilderness/dam_control.yaml
+triggers:
+  - on_flag: floodgate_open
+    steps:
+      - broadcast: "Ancient gears grind as the floodgate slowly opens..."
+      - delay: 15
+        broadcast: "Water thunders through the opening!"
+      - set_flags:
+          valley_flooded: true
+```
+
+Because this watches a **world** flag (`on_flag`), it fires once globally when
+the flag is first set — not per-player. Everyone in the room sees the messages.
+
+#### Example 4: "Push button" — trigger that resets itself
+
+A player pulls a lever. The trigger fires, then clears the flag so it can be
+pulled again. This simulates a toggle without needing a separate mechanism:
+
+```yaml
+triggers:
+  - on_player_flag: lever_pulled
+    steps:
+      - broadcast: "The lever snaps back into place with a loud clunk."
+      - set_player_flags:
+          lever_pulled: false      # reset so next pull re-fires
+```
+
+---
+
+### Global Triggers
+
+Global triggers live in `data/triggers/`. They fire regardless of where the
+flag-setting player is located. Use them for server-wide events.
+
+#### Example 5: Level-up announcement
+
+When a player reaches level 99 in any skill, announce it server-wide.
+The game code sets `announce_99_skill` = the skill name (e.g. `"attack"`):
+
+```yaml
+# data/triggers/announce_99.yaml
+on_player_flag: announce_99_skill
+steps:
+  - broadcast_global: "%p has reached level 99 %v!"
+```
+
+`%p` expands to the player's name, `%v` expands to the flag value (`"attack"`,
+`"mining"`, etc.):
+
+```
+PlayerName has reached level 99 attack!
+```
+
+#### Example 6: World-first boss kill — global broadcast
+
+A boss mob's death sets world flag `world_boss_slain`. A global trigger
+announces it to everyone:
+
+```yaml
+# data/triggers/world_boss_slain.yaml
+on_flag: world_boss_slain
+steps:
+  - broadcast_global: "The Ancient One has been vanquished! The land stirs with new life."
+  - set_flags:
+      ancient_lands_access: true      # opens a zone for everyone
+```
+
+#### Example 7: Global trigger with room context
+
+A global trigger can specify a `room` for broadcasts and mob spawns. This is
+useful when a world flag should trigger effects in a specific location:
+
+```yaml
+# data/triggers/obelisk_activated.yaml
+on_flag: desert_obelisk_charged
+room: 1200
+steps:
+  - broadcast: "The obelisk hums with stored power."
+  - delay: 30
+    broadcast: "A beam of light shoots from the obelisk into the sky!"
+  - spawn_mob: obelisk_guardian
+```
+
+---
+
+### Cascading Triggers
+
+When a trigger step sets a flag, any triggers watching that flag fire immediately
+(on the next tick). This lets you chain sequences together:
+
+```yaml
+triggers:
+  - on_player_flag: phase_1_done
+    steps:
+      - broadcast: "The first seal cracks."
+      - set_player_flags:
+          phase_2_started: true       # triggers the next trigger
+
+  - on_player_flag: phase_2_started
+    steps:
+      - delay: 10
+        broadcast: "The second seal glows brighter..."
+      - delay: 10
+        spawn_mob: phase_2_adds
+```
+
+Both sequences run concurrently — phase 2's delay countdown starts on the same
+tick phase 1 completes.
+
+**Self-re-triggering is prevented.** A trigger can't fire itself again while
+its sequence is already in progress (tracked per-player per-trigger-ID). Two
+different triggers watching the same flag both fire independently.
+
+---
+
+### Transient Mobs
+
+Mobs spawned via `spawn_mob` in a trigger step are **transient** — they exist
+until killed or despawned, but do **not** respawn. They behave exactly like
+regular mobs: they can be attacked, talked to, examined, and stolen from.
+
+#### SpawnMobConfig
+
+`spawn_mob` accepts either a simple string (mob ID only) or a full config map:
+
+```yaml
+spawn_mob: altar_guardian
+
+# Equivalent to:
+spawn_mob:
+  id: altar_guardian
+```
+
+Full config:
+
+| Field              | Default      | Description                                                                                                                                   |
+| ------------------ | ------------ | --------------------------------------------------------------------------------------------------------------------------------------------- |
+| `id`               | *(required)* | Mob definition ID from `data/mobs/`.                                                                                                          |
+| `owner_only`       | `false`      | Only the triggering player can interact (attack, talk, steal). Non-owners see "They don't seem interested in you." Everyone can still `look`. |
+| `despawn_on_leave` | `false`      | If `true`, the mob despawns when the owner leaves the allowed rooms.                                                                          |
+| `despawn_rooms`    | spawn room   | Rooms the owner can be in without triggering despawn. Empty = the spawn room only.                                                            |
+| `despawn_ticks`    | `0`          | Tick countdown after owner leaves despawn_rooms. `0` = immediate removal. Owner returning resets the countdown.                               |
+
+#### Example 8: Personal boss — despawns if you leave the arena
+
+```yaml
+spawn_mob:
+  id: arena_champion
+  owner_only: true
+  despawn_on_leave: true
+  despawn_ticks: 60        # 60-tick grace period if you step out
+```
+
+#### Example 9: Persistent NPC — stays until killed
+
+```yaml
+spawn_mob:
+  id: wandering_merchant
+  # despawn_on_leave defaults to false — stays forever
+```
+
+#### Example 10: Despawning via trigger step
+
+Use `despawn_mob` in a step to remove previously spawned mobs:
+
+```yaml
+triggers:
+  - on_player_flag: puzzle_solved
+    steps:
+      - despawn_mob: puzzle_guardian       # remove the puzzle mob
+      - delay: 10
+        broadcast: "The guardian dissolves into mist."
+      - spawn_mob: boss_guardian           # spawn the real boss
+```
+
+`despawn_mob` with an owner only removes mobs spawned by that player. Without an
+owner (in world-flag triggers), it removes all matching mobs.
+
+#### Example 11: Fixed-lifetime mob
+
+A mob that exists for exactly 2 minutes regardless of owner location:
+
+```yaml
+steps:
+  - spawn_mob:
+      id: timed_challenge_mob
+      owner_only: true
+  - delay: 200                    # 200 ticks = 2 minutes
+    despawn_mob: timed_challenge_mob
+    broadcast: "The challenge ends. The mob vanishes."
+```
+
+---
+
+### Template Variables
+
+Steps that send text support these variables:
+
+| Variable | Expands to |
+|---|---|
+| `%p` | Player name (only available for `on_player_flag` triggers) |
+| `%v` | Flag value at the time the trigger fired (e.g. the skill name for level-up announcements) |
+
+```yaml
+steps:
+  - broadcast_global: "%p has completed %v!"
+  # Renders: "Alice has completed the Gauntlet!"
+```
+
+---
+
+### Value-Matching Triggers
+
+By default a trigger fires when the watched flag becomes truthy. Add `value:` to
+require a specific value:
+
+```yaml
+# Only fires when quest_stage reaches exactly 3
+triggers:
+  - on_player_flag: quest_stage
+    value: 3
+    steps:
+      - message: "Stage 3 begins — the temple doors swing open."
+      - set_flags:
+          temple_open: true
+```
+
+This enables multi-stage quests where the same flag advances through numeric
+stages, and different triggers fire at different values.
+
+```yaml
+triggers:
+  - on_player_flag: quest_stage
+    value: 1
+    steps:
+      - message: "Quest started — find the crystal shard."
+  - on_player_flag: quest_stage
+    value: 2
+    steps:
+      - message: "You found the shard — return to the elder."
+  - on_player_flag: quest_stage
+    value: 3
+    steps:
+      - message: "The ritual begins..."
+      - delay: 10
+        broadcast: "The temple hums with ancient power!"
+      - spawn_mob: crystal_guardian
+```
+
+---
+
+### Full Scenario: Multi-Room Investigation Quest
+
+A player investigates a murder scene across several rooms. Finding clues in order
+advances a numeric flag through stages. The last stage spawns a boss.
+
+**Step 1: The body — sets `investigation: 1`**
+
+```yaml
+# data/objects/unique/5001_body.yaml
+name: body
+on_look:
+  set_player_flags:
+    investigation: 1
+```
+
+**Step 2: Blood trail in room 5002** — room trigger fires on value 1
+
+```yaml
+# data/rooms/city/5002_alley.yaml
+triggers:
+  - on_player_flag: investigation
+    value: 1
+    steps:
+      - delay: 3
+        message: "You notice a trail of blood leading east..."
+      - set_player_flags:
+          investigation: 2
+```
+
+**Step 3: Broken dagger in room 5003** — room trigger fires on value 2
+
+```yaml
+# data/rooms/city/5003_warehouse.yaml
+triggers:
+  - on_player_flag: investigation
+    value: 2
+    steps:
+      - delay: 3
+        message: "A glint of metal catches your eye under a crate."
+```
+
+**Step 4: Confrontation** — room trigger fires on value 3 (set by a separate talk node), spawns boss
+
+```yaml
+# data/rooms/city/5004_docks.yaml
+triggers:
+  - on_player_flag: investigation
+    value: 3
+    steps:
+      - delay: 5
+        broadcast: "A shadow detaches itself from the warehouse wall..."
+      - delay: 5
+        broadcast: "The assassin steps into the light, blade drawn."
+      - spawn_mob:
+          id: assassin_boss
+          owner_only: true
+          despawn_on_leave: true
+          despawn_rooms: [5004]
+```
+
+The player must stay in room 5004 to fight the boss. If they flee, the boss
+despawns and the flag stays at 3 — they can't re-trigger anything because the
+flag is already at that value.
+
+---
+
+### Full Scenario: Server-Wide World Event
+
+A server event progresses through stages. A global trigger chains world flags to
+advance the event for everyone.
+
+**Phase 1 trigger:**
+
+```yaml
+# data/triggers/event_phase1.yaml
+on_flag: event_phase1_start
+steps:
+  - broadcast_global: "The sky darkens as an eclipse begins..."
+  - delay: 100
+    set_flags:
+      event_phase2_start: true
+```
+
+**Phase 2 trigger:**
+
+```yaml
+# data/triggers/event_phase2.yaml
+on_flag: event_phase2_start
+steps:
+  - broadcast_global: "Monsters pour from the shadows across the land!"
+  - delay: 300
+    set_flags:
+      event_phase3_start: true
+```
+
+**Phase 3 trigger — event ends:**
+
+```yaml
+# data/triggers/event_phase3.yaml
+on_flag: event_phase3_start
+steps:
+  - broadcast_global: "The eclipse passes. The monsters retreat."
+  - delay: 50
+    set_flags:
+      event_active: false
+```
+
+GM commands or admin tools set `event_phase1_start: true` to kick things off.
+The cascade handles the rest.
+
+---
+
+### How Flags Get Set
+
+Triggers fire whenever a flag changes — it doesn't matter *how* the flag was set.
+All of these paths activate triggers:
+
+| Source | Example |
+|---|---|
+| Object `on_look` | `look sign` sets `1001_look_sign: true` |
+| Talk node actions | NPC sets `quest_started: true` after accepting |
+| Talk option actions | Player selects a choice that sets a flag |
+| On-enter steps | Room entry sets `1001_welcome: true` |
+| Exit traversal | Walking through an exit sets `boarded_shuttle: true` |
+| Use interactions | `push button` sets `gate_open: true` |
+| Trigger steps | One trigger chain-sets a flag for another trigger |
+
+---
+
+### Trigger Firing Rules
+
+1. **Only on actual value change.** Setting `true` → `true` is a no-op. Setting
+   `1` → `2` fires if a trigger watches that flag. Setting `nil` → `true` fires.
+   Setting `true` → `false` does **not** fire (triggers activate on becoming
+   truthy, not on becoming falsy).
+
+2. **Conditions are not re-evaluated.** A trigger's steps always run once the
+   trigger fires. There is no per-step condition checking (unlike `on_enter`).
+
+3. **Per-player per-trigger-ID.** The same player can't have two instances of
+   the same trigger running simultaneously. Starting a new one replaces the old.
+
+4. **Player must be online.** Player-flag triggers only fire for connected
+   players. World-flag triggers fire regardless.
+
+5. **Room triggers check room.** Room-level triggers only fire when the
+   flag-setting player is in that room. This keeps local events local.
+
+6. **Cascading triggers run concurrently.** If trigger A sets a flag that
+   activates trigger B, both sequences advance on each tick independently.
+
+---
+
+### Validation
+
+Startup validation checks that trigger `spawn_mob.id` references an existing mob
+definition, `give_item`/`take_item` reference existing items, `teleport` and
+`despawn_rooms` reference existing rooms, and that global trigger IDs are unique.
+
+Validation does NOT check that the watched flags (`on_player_flag` / `on_flag`)
+are ever set — those are dynamic, set by runtime gameplay, and can't be statically
+verified.