OnStart takes a script name, and OnFinale joins it

The opening a game plays was the one piece of content that had to be
assembled in the wiring, because OnStart wanted an Action. It takes the
name of a registered Script now, so an opening is a Script like any
other, and Validate rejects a name that is not there.

OnFinale names the closing script and queues it straight after the start
one — what a "boot into the ending" debug flag wants.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.woodpecker.yaml

@@ -0,0 +1,12 @@
+# A könyvtárnak nincs teszt-suite-ja, ezért a regressziót a fordítás és a
+# `go vet` fogja meg. Az ebitengine builder image kell hozzá: az Ebitengine
+# Linuxon cgo-t használ, tehát a fordításhoz X11/GL/ALSA fejlécek kellenek.
+steps:
+  - name: test
+    image: git.teletypegames.org/build/ebitengine-builder:latest
+    commands:
+      - go version
+      - echo "==> go build"
+      - go build ./...
+      - echo "==> go vet"
+      - go vet ./...

README.md

@@ -30,14 +30,15 @@ import "git.teletypegames.org/games/inkwell"
 6. [Entity reference](#6-entity-reference)
    - 6.1 [Asset](#61-asset)
    - 6.2 [Scene](#62-scene)
-   - 6.3 [Hotspot](#63-hotspot)
+   - 6.3 [Exit](#63-exit)
-   - 6.4 [Trigger](#64-trigger)
+   - 6.4 [Hotspot](#64-hotspot)
-   - 6.5 [Item](#65-item)
+   - 6.5 [Trigger](#65-trigger)
-   - 6.6 [Inventory](#66-inventory)
+   - 6.6 [Item](#66-item)
-   - 6.7 [Character](#67-character)
+   - 6.7 [Inventory](#67-inventory)
-   - 6.8 [Dialogue](#68-dialogue)
+   - 6.8 [Character](#68-character)
-   - 6.9 [Script](#69-script)
+   - 6.9 [Dialogue](#69-dialogue)
-   - 6.10 [Verb](#610-verb)
+   - 6.10 [Script](#610-script)
+   - 6.11 [Verb](#611-verb)
 7. [The action system](#7-the-action-system)
    - 7.1 [Action and Runner](#71-action-and-runner)
    - 7.2 [Status and Ctx](#72-status-and-ctx)
@@ -188,11 +189,13 @@ type ThemeManager      = Manager[Theme]
 | Method                 | Behaviour                                                  |
 |------------------------|------------------------------------------------------------|
 | `Register(v T)`        | Adds `v` to the registry. Panics on empty or duplicate `Name`. |
+| `Set(v T)`             | Replaces an entry in place, keeping its position; registers it when the name is new. |
 | `Get(name) (T, bool)`  | Looks up by name. The boolean is `false` if absent.        |
 | `MustGet(name) T`      | Same as `Get`, but panics on missing names.                |
 | `Has(name) bool`       | True if the name is registered.                            |
 | `Len() int`            | Number of registered entries.                              |
 | `Names() []string`     | Returns names in **insertion order** (used for widget Z-order). |
+| `All() []T`            | Returns every entry in **insertion order**.                |
 | `SortedNames() []string` | Returns names alphabetically.                            |
 | `Each(fn func(T))`     | Iterates in insertion order.                               |
 | `Remove(name string)`  | Drops a registration; silent no-op if unknown.             |
@@ -215,6 +218,11 @@ on startup. Crashing loudly during `Build()` surfaces the problem in
 development; quietly accepting the second registration would silently mask
 shadowed entities at runtime.
 
+When a registration genuinely has to be rewritten — a derived field filled in
+after the fact, a hot-reloaded entity — `Set` is the deliberate overwrite. It
+keeps the entry's place in the insertion order, so widget Z-order and any other
+order-sensitive iteration survive the rewrite.
+
 ---
 
 ## 4. The Game aggregate
@@ -237,6 +245,11 @@ type Game struct {
     UIManager        *UIManager
     ThemeManager     *ThemeManager
 
+    // exits
+    SceneRect Rectangle          // the part of the window the picture occupies
+    ExitLook  func(Exit) Action  // default look response for generated exits
+    ExitTake  func(Exit) Action  // default take response for generated exits
+
     // runtime services
     State     *State
     Inventory *Inventory
@@ -262,16 +275,50 @@ selects `classic-scumm` as the active theme. Widgets are **not**
 auto-registered — call `RegisterDefaultUI(g)` (or one of its siblings)
 explicitly, or let `Run` install the default set if `UIManager` is empty.
 
+The manager fields are ordinary `*Manager` values, so a domain that keeps its
+own registries can **assign them onto the Game** instead of copying every entry
+across:
+
+```go
+g := inkwell.NewGame("Real World", 640, 380)
+g.SceneManager = mySceneManager
+g.AssetManager = myAssetManager
+```
+
+Do it before `Run` — that is where the engine wires up the parts that hold a
+registry directly, so whichever managers the `*Game` carries by then are the
+ones that get used. Two of them are worth a second thought before replacing:
+`ThemeManager` arrives holding the four presets and `classic-scumm` selected,
+and `VerbManager` the four SCUMM verbs. Replacing either throws that away —
+register into them instead unless that is what you want.
+
 ### 4.2 Lifecycle hooks
 
 ```go
 func (g *Game) StartAt(name string) *Game     // entry scene
-func (g *Game) OnStart(a Action) *Game        // action run after the scene's OnEnter
+func (g *Game) OnStart(script string) *Game   // script run after the scene's OnEnter
+func (g *Game) OnFinale(script string) *Game  // closing script, queued after OnStart
 func (g *Game) Validate() error               // cross-check name references
 func (g *Game) Run() error                    // same as inkwell.Run(g)
 ```
 
-`StartAt` and `OnStart` return `*Game` so they chain at the end of `Build`.
+`OnStart` and `OnFinale` name registered scripts rather than taking an action,
+so the opening a game plays is content like any other — a `Script` in the
+`ScriptManager`, reachable by name and editable without touching the wiring.
+`Validate` rejects a name that is not registered.
+
+`OnFinale` is queued directly after the start script, which is what a "boot
+straight into the ending" debug flag wants:
+
+```go
+g.StartAt(start)
+g.OnStart(ScriptOpening)
+if finale {
+    g.OnFinale(ScriptFinale)
+}
+```
+
+All three return `*Game` so they chain at the end of `Build`.
 
 ### 4.3 Theme accessors
 
@@ -330,11 +377,28 @@ func (g *Game) Messages() []LogMessage
 ### 4.6 Scene helpers
 
 ```go
+func (g *Game) CurrentScene() string
+func (g *Game) PreviousScene() string
+func (g *Game) SceneArea() Rectangle
+func (g *Game) SceneHotspots(name string) []Hotspot
+func (g *Game) HotspotAt(p Point) *Hotspot
 func (g *Game) CharacterInScene(name string) bool
 ```
 
-Used by `CharacterPanel` to auto-hide when its character isn't an actor in
+`CurrentScene` is where the player is, empty before the first scene is
-the current scene.
+entered; `PreviousScene` is the one before it, which is where
+[`Back()`](#73-built-in-actions) leads. Both survive a save.
+
+`SceneArea` is `SceneRect`, or the whole window when it was never set. It is
+what [exit strips](#63-exit) are measured against.
+
+`SceneHotspots` is everything clickable in a scene: its own `Hotspots` first,
+then one per `Exit`. Authored hotspots come first because the engine takes the
+first area that contains the click, so a painted thing beats the edge strip an
+exit sits on wherever the two overlap. The expansion is cached per scene.
+
+`CharacterInScene` is used by `CharacterPanel` to auto-hide when its character
+isn't an actor in the current scene.
 
 ### 4.7 Text drawing hook
 
@@ -428,6 +492,7 @@ type Scene struct {
     Background string         // Asset.Name
     Music      string         // Asset.Name (optional)
     Hotspots   []Hotspot
+    Exits      []Exit         // connections to other scenes
     Walkboxes  []Polygon
     Triggers   []Trigger
     Actors     []SceneActor
@@ -450,12 +515,84 @@ routes through a BFS over the polygon adjacency graph (polygons that
 share an edge are neighbours), with the midpoint of each shared edge
 used as a waypoint. Destinations outside every walkbox are clipped to
 the nearest boundary. With no walkboxes the character walks in a
-straight line — see [§6.7](#67-character) and [§15.4](#154-character-movement).
+straight line — see [§6.8](#68-character) and [§15.4](#154-character-movement).
 
 `Triggers` fire on the rising edge of their `When` condition. The
-engine samples each trigger once per idle frame; see [§6.4](#64-trigger).
+engine samples each trigger once per idle frame; see [§6.5](#65-trigger).
 
-### 6.3 Hotspot
+`Exits` are the scene's connections to other scenes, declared as data. The
+engine turns each one into a hotspot — see [§6.3](#63-exit).
+
+### 6.3 Exit
+
+```go
+// inkwell/scene.exit.go
+
+type Exit struct {
+    To      string      // target scene; empty means "back the way you came"
+    Label   string      // what the status line calls it
+    Side    ExitSide    // where it sits when Area is nil
+    Area    Shape       // overrides the edge strip Side would give it
+    Needs   string      // flag that has to be set before it opens
+    Blocked Action      // what happens while it is not
+    OnLook  Action      // overrides Game.ExitLook for this exit
+    OnTake  Action      // overrides Game.ExitTake for this exit
+}
+
+type ExitSide int
+const (
+    ExitLeft  ExitSide = iota // off the left edge
+    ExitRight                 // off the right edge
+    ExitBack                  // into the depth of the picture
+    ExitNear                  // out towards the camera
+)
+
+func ExitName(to string) string
+```
+
+A connection belongs to the scene it leads out of, so it is written in that
+scene's own literal rather than in a map kept somewhere else:
+
+```go
+Scene{
+    Name: "alley",
+    Exits: []Exit{
+        {To: "noodle_house", Label: "back out to the street", Side: ExitLeft},
+        {To: "", Label: "the fire escape", Side: ExitBack,
+         Needs: "has_ladder", Blocked: Say("paul", "Can't reach it.")},
+    },
+}
+```
+
+The engine expands each exit into a `Hotspot` with `Cursor: CursorExit`, the
+exit's `Label`, `OnUse` bound to `GoTo(To)` — or [`Back()`](#73-built-in-actions)
+when `To` is empty — and, when `Needs` is set, the whole travel wrapped in
+`If(Flag(Needs), travel, Blocked)`. The exit is visible either way: a locked
+door still says it is a door.
+
+`OnLook` and `OnTake` are usually not written per exit. `Game.ExitLook` and
+`Game.ExitTake` supply them for every exit in the game, so the phrasing lives
+in one place:
+
+```go
+g.ExitLook = func(e Exit) Action { return Say("paul", "That way: "+e.Label+".") }
+g.ExitTake = func(e Exit) Action { return Say("paul", "It's a way out, not a thing.") }
+```
+
+**Placement.** With no `Area`, an exit is a strip along one edge of the
+picture, sized as a fraction of [`Game.SceneArea()`](#46-scene-helpers) — the
+convention every 1990s point & click used, and one field to re-aim at a real
+door once the artwork is measured. A game whose HUD covers the foot of the
+window sets `Game.SceneRect`, so the strips land inside the painting instead of
+under the HUD.
+
+**The graph stays readable.** The generated hotspot is named
+`ExitName(To)` — `"exit:noodle_house"`, or `"exit:back"` — so the location
+graph can be read straight back out of the registered scenes, and
+[`Validate`](#17-validation) rejects an exit that names a scene nobody
+registered.
+
+### 6.4 Hotspot
 
 ```go
 // inkwell/scene.hotspot.go
@@ -497,7 +634,7 @@ resolves a click via `hotspot.handler(verbName)` which maps the four
 built-in verbs to their `On*` fields and falls back to `OnVerb[verbName]`
 for custom verbs.
 
-### 6.4 Trigger
+### 6.5 Trigger
 
 ```go
 // inkwell/scene.trigger.go
@@ -522,7 +659,7 @@ frame — the edge is preserved across the busy window. Save/Load resets
 trigger state to "freshly armed", matching the behaviour of scene
 re-entry.
 
-### 6.5 Item
+### 6.6 Item
 
 ```go
 // inkwell/item.def.go
@@ -545,7 +682,7 @@ hotspot with an item selected resolves the action via, in order:
 2. `item.OnUseWith[hotspot.Name]`
 3. Otherwise the engine flashes "Nem ehhez." and deselects.
 
-### 6.6 Inventory
+### 6.7 Inventory
 
 ```go
 // inkwell/item.inventory.go
@@ -564,7 +701,7 @@ func (i *Inventory) Items() []string           // copy
 Not a manager — pure runtime state owned by `Game`. Mutated by actions
 (`Give`, `TakeAway`) and by the `InventoryBar` widget on click.
 
-### 6.7 Character
+### 6.8 Character
 
 ```go
 // inkwell/actor.def.go
@@ -605,7 +742,7 @@ Movement is driven by the `Walk` action and `Game.tickCharacters` —
 stepping at `Speed` pixels/sec (default 60) along the waypoint list
 computed by [walkbox routing](#62-scene).
 
-### 6.8 Dialogue
+### 6.9 Dialogue
 
 ```go
 // inkwell/dialog.def.go
@@ -647,7 +784,7 @@ The dialog flow:
 5. `EndDialogue()` closes the conversation; `GotoNode("other")` jumps to
    another node in the same dialogue.
 
-### 6.9 Script
+### 6.10 Script
 
 ```go
 // inkwell/action.script.go
@@ -662,7 +799,7 @@ A `Script` is just a named composite action — useful when you want to
 reuse a cutscene (intro, victory, transition) from multiple call sites.
 Fire one with `RunScript("name")`.
 
-### 6.10 Verb
+### 6.11 Verb
 
 ```go
 // inkwell/ui.verb.go
@@ -749,6 +886,7 @@ type Ctx struct {
 | `Wait(seconds float64) Action`           | Block the runner for `seconds`.                                            |
 | `Say(speaker, text string) Action`       | Show the line above the speaker (`SpeechBubble`), append to chat-log. Click-to-skip. Duration scales with text length, 1.2s floor. |
 | `GoTo(scene string) Action`              | Switch the current scene via a fade transition.                            |
+| `Back() Action`                          | Return to `PreviousScene()`. No-op when there is nowhere to go back to.    |
 | `Walk(character string, to Point) Action`| Move a character to `to` at `Character.Speed`. Returns when arrived.       |
 | `Give(item string) Action`               | Add `item` to inventory.                                                   |
 | `TakeAway(item string) Action`           | Remove `item` from inventory.                                              |
@@ -1413,13 +1551,15 @@ func Run(g *Game) error                          // toplevel — same as g.Run()
 
 `Run` does, in order:
 
-1. `g.Validate()` — cross-check name references between managers.
+1. `g.Audio.attach(g.AssetManager)` — wire the audio player to whichever
-2. If `UIManager` is empty, call `RegisterDefaultUI(g)`.
+   asset registry the game is carrying by now.
-3. Place the start scene directly (no transition), bump
+2. `g.Validate()` — cross-check name references between managers.
+3. If `UIManager` is empty, call `RegisterDefaultUI(g)`.
+4. Place the start scene directly (no transition), bump
    `State.NoteVisit`, position registered actors, kick off music.
-4. Compose `Seq(scene.OnEnter, game.OnStart)` and queue it as the initial
+5. Compose `Seq(scene.OnEnter, OnStart script, OnFinale script)` and queue
-   action — the first script tick runs both in order.
+   it as the initial action — the first script tick runs them in order.
-5. `ebiten.SetWindowSize(Width*4, Height*4)`,
+6. `ebiten.SetWindowSize(Width*4, Height*4)`,
    `ebiten.SetWindowTitle(g.Title)`, then `ebiten.RunGame(&engine{g})`.
 
 ### 15.1 `engine.Update`
@@ -1530,6 +1670,8 @@ It cross-checks:
   `Asset`.
 - Optional `Scene.Music` (if non-empty) references a registered `Asset`.
 - Every `SceneActor.CharacterName` is a registered character.
+- Every `Scene.Exit.To` names a registered scene (empty is allowed — it
+  means "back the way you came").
 - An active theme is selected and registered.
 
 Returns the first error wrapping one of the `Err...` sentinels (so callers
@@ -1551,7 +1693,7 @@ Slots are written as JSON files under `g.SaveDir` (default `saves/`,
 relative to the working directory), one file per slot named
 `slot<N>.json`. The save captures the **mutable runtime state**:
 
-- `currentScene`, the active verb, and the active theme.
+- `currentScene` and `previousScene`, the active verb, and the active theme.
 - Every character's position, target, and moving flag.
 - The full `State`: flags, vars, visited and talked counters.
 - The inventory item list plus the currently selected slot.
@@ -1675,6 +1817,7 @@ inkwell/                            # module git.teletypegames.org/games/inkwell
 ├── scene.def.go                   # Scene, SceneActor
 ├── scene.manager.go               # SceneManager alias
 ├── scene.hotspot.go               # Hotspot, CursorKind
+├── scene.exit.go                  # Exit, ExitSide + edge-strip geometry
 ├── scene.trigger.go               # Trigger + rising-edge engine sweep
 ├── scene.path.go                  # walkbox routing (BFS over polygon adjacency)
 ├── scene.transition.go            # fade-to-black overlay (internal)

action.def.go

@@ -250,6 +250,24 @@ func (a *gotoAction) Tick(ctx *Ctx) Status {
 	return StatusDone
 }
 
+// ----- Back -------------------------------------------------------------
+
+type backAction struct{}
+
+// Back returns to the scene the player came from. Most exits name their
+// destination, because a door leads where it leads; a scene reached from
+// several different rooms cannot, so its way out is a direction, not a place.
+// A no-op when there is nowhere to go back to.
+func Back() Action { return backAction{} }
+
+func (a backAction) Start() Runner { return a }
+func (a backAction) Tick(ctx *Ctx) Status {
+	if prev := ctx.Game.PreviousScene(); prev != "" {
+		ctx.Game.changeScene(prev)
+	}
+	return StatusDone
+}
+
 // ----- inventory --------------------------------------------------------
 
 type giveAction struct{ item string }

core.dsl.go

@@ -7,6 +7,10 @@ import (
 // Run validates the game, then enters the ebiten main loop. The window is
 // sized to 4× the internal resolution.
 func Run(g *Game) error {
+	// The domain may have swapped a manager in since NewGame, so the parts
+	// that hold a registry directly are wired here, not at construction.
+	g.Audio.attach(g.AssetManager)
+
 	if err := g.Validate(); err != nil {
 		return err
 	}
@@ -30,8 +34,11 @@ func Run(g *Game) error {
 	if s.OnEnter != nil {
 		seq = append(seq, s.OnEnter)
 	}
-	if g.onStart != nil {
+	if g.onStart != "" {
-		seq = append(seq, g.onStart)
+		seq = append(seq, RunScript(g.onStart))
+	}
+	if g.onFinale != "" {
+		seq = append(seq, RunScript(g.onFinale))
 	}
 	if len(seq) > 0 {
 		g.queueAction(Seq(seq...), "init")

core.game.go

@@ -24,6 +24,17 @@ type Game struct {
 	UIManager        *UIManager
 	ThemeManager     *ThemeManager
 
+	// SceneRect is the part of the window the picture occupies. Zero means
+	// the whole window. A game with a HUD along the foot sets it, so that
+	// generated exit strips (see scene.exit.go) land inside the painting.
+	SceneRect Rectangle
+
+	// ExitLook and ExitTake supply the default look and take responses for
+	// every hotspot generated from Scene.Exits. Nil means no response.
+	// An Exit can override either one.
+	ExitLook func(Exit) Action
+	ExitTake func(Exit) Action
+
 	State     *State
 	Inventory *Inventory
 	Audio     *AudioPlayer
@@ -31,12 +42,15 @@ type Game struct {
 	Input     *Input
 
 	startID     string
-	onStart     Action
+	onStart     string
+	onFinale    string
 	activeTheme string
 
 	// runtime
 	loaded        *loadedAssets
 	currentScene  string
+	previousScene string
+	exitHotspots  map[string][]Hotspot
 	chars         map[string]*runtimeChar
 	scriptRunner  Runner
 	scriptCtx     *Ctx
@@ -101,6 +115,10 @@ type runtimeDialog struct {
 // NewGame initializes a game with empty entity managers, the SCUMM-style
 // verb set, all preset themes, and "classic-scumm" selected. Widgets are
 // NOT auto-registered — call RegisterDefaultUI(g) explicitly.
+//
+// A domain is free to replace any of the entity managers with one of its
+// own before Run — the registries are ordinary *Manager values, and Run
+// wires the engine to whichever ones the Game holds by then.
 func NewGame(title string, w, h int) *Game {
 	g := &Game{
 		Title:            title,
@@ -125,7 +143,6 @@ func NewGame(title string, w, h int) *Game {
 		transition:       &transition{},
 		selectedVerb:     "look",
 	}
-	g.Audio.attach(g.AssetManager)
 	for _, v := range defaultVerbs() {
 		g.VerbManager.Register(v)
 	}
@@ -135,7 +152,54 @@ func NewGame(title string, w, h int) *Game {
 }
 
 func (g *Game) StartAt(name string) *Game { g.startID = name; return g }
-func (g *Game) OnStart(a Action) *Game    { g.onStart = a; return g }
+
+// CurrentScene is the scene the player is in, empty before the first one is
+// entered. PreviousScene is the one before it, which is where Back() leads.
+func (g *Game) CurrentScene() string  { return g.currentScene }
+func (g *Game) PreviousScene() string { return g.previousScene }
+
+// SceneArea is SceneRect, or the whole window when it was never set.
+func (g *Game) SceneArea() Rectangle {
+	if g.SceneRect.W > 0 && g.SceneRect.H > 0 {
+		return g.SceneRect
+	}
+	return Rect(0, 0, float64(g.Width), float64(g.Height))
+}
+
+// SceneHotspots is everything clickable in a scene: its own hotspots first,
+// then one per Exit. Authored hotspots come first because the engine takes the
+// first area that contains the click, so a painted thing beats the edge strip
+// an exit sits on wherever the two overlap.
+//
+// The expansion is cached, so the pointers HotspotAt hands out stay valid.
+func (g *Game) SceneHotspots(name string) []Hotspot {
+	if hs, ok := g.exitHotspots[name]; ok {
+		return hs
+	}
+	s, ok := g.SceneManager.Get(name)
+	if !ok {
+		return nil
+	}
+	hs := make([]Hotspot, 0, len(s.Hotspots)+len(s.Exits))
+	hs = append(hs, s.Hotspots...)
+	for _, e := range s.Exits {
+		hs = append(hs, e.hotspot(g))
+	}
+	if g.exitHotspots == nil {
+		g.exitHotspots = make(map[string][]Hotspot)
+	}
+	g.exitHotspots[name] = hs
+	return hs
+}
+
+// OnStart names the script queued after the start scene's OnEnter, once,
+// when the game boots.
+func (g *Game) OnStart(script string) *Game { g.onStart = script; return g }
+
+// OnFinale names the game's closing script, queued directly after the start
+// script — which is what a "boot straight into the ending" debug flag wants.
+// Leave it unset for an ordinary run.
+func (g *Game) OnFinale(script string) *Game { g.onFinale = script; return g }
 
 // ----- theme + UI conveniences ------------------------------------------
 
@@ -194,9 +258,9 @@ func (g *Game) HotspotAt(p Point) *Hotspot {
 	if g.currentScene == "" {
 		return nil
 	}
-	s := g.SceneManager.MustGet(g.currentScene)
+	hs := g.SceneHotspots(g.currentScene)
-	for i := range s.Hotspots {
+	for i := range hs {
-		h := &s.Hotspots[i]
+		h := &hs[i]
 		if h.Area != nil && h.Area.Contains(p) {
 			return h
 		}
@@ -266,6 +330,16 @@ func (g *Game) Validate() error {
 				return fmt.Errorf("%w: scene %q actor %q", ErrUnknownCharacter, name, a.CharacterName)
 			}
 		}
+		for _, e := range s.Exits {
+			if e.To != "" && !g.SceneManager.Has(e.To) {
+				return fmt.Errorf("%w: scene %q exit to %q", ErrUnknownScene, name, e.To)
+			}
+		}
+	}
+	for _, name := range []string{g.onStart, g.onFinale} {
+		if name != "" && !g.ScriptManager.Has(name) {
+			return fmt.Errorf("%w: %q", ErrUnknownScript, name)
+		}
 	}
 	if g.activeTheme == "" || !g.ThemeManager.Has(g.activeTheme) {
 		return fmt.Errorf("inkwell: no active theme (got %q)", g.activeTheme)
@@ -309,6 +383,9 @@ func (g *Game) changeScene(name string) {
 	}
 	prev := g.currentScene
 	g.transition.start(func() {
+		if prev != "" && prev != name {
+			g.previousScene = prev
+		}
 		if prev != "" {
 			old := g.SceneManager.MustGet(prev)
 			if old.OnLeave != nil {

core.manager.go

@@ -33,6 +33,18 @@ func (m *Manager[T]) Register(v T) {
 	m.order = append(m.order, name)
 }
 
+// Set replaces a registered entry in place, keeping its position in the
+// registration order, and registers the entry when the name is new. Register
+// panics on a duplicate; Set is the deliberate overwrite.
+func (m *Manager[T]) Set(v T) {
+	name := v.GetName()
+	if _, ok := m.items[name]; !ok {
+		m.Register(v)
+		return
+	}
+	m.items[name] = v
+}
+
 func (m *Manager[T]) Get(name string) (T, bool) {
 	v, ok := m.items[name]
 	return v, ok
@@ -59,6 +71,15 @@ func (m *Manager[T]) Names() []string {
 	return append([]string(nil), m.order...)
 }
 
+// All returns every registered entry in insertion order.
+func (m *Manager[T]) All() []T {
+	out := make([]T, len(m.order))
+	for i, n := range m.order {
+		out[i] = m.items[n]
+	}
+	return out
+}
+
 func (m *Manager[T]) SortedNames() []string {
 	names := append([]string(nil), m.order...)
 	sort.Strings(names)

scene.def.go

@@ -6,6 +6,7 @@ type Scene struct {
 	Background string // Asset.Name
 	Music      string // Asset.Name (optional)
 	Hotspots   []Hotspot
+	Exits      []Exit // connections to other scenes; see scene.exit.go
 	Walkboxes  []Polygon
 	Triggers   []Trigger
 	Actors     []SceneActor

scene.exit.go

@@ -0,0 +1,121 @@
+package inkwell
+
+// ExitSide is where on the picture an exit sits when it has no Area of its
+// own: off one edge, into the depth of the picture, or out towards the
+// camera. Until the doors are measured on the artwork, an edge strip is the
+// convention every 1990s point & click used, and re-aiming an exit at a real
+// door later is a one-field change.
+type ExitSide int
+
+const (
+	ExitLeft  ExitSide = iota // off the left edge
+	ExitRight                 // off the right edge
+	ExitBack                  // into the depth of the picture
+	ExitNear                  // out towards the camera
+)
+
+// Exit is one way out of a scene. The engine turns it into a Hotspot, so a
+// connection can be declared as data — where it leads, what the status line
+// calls it, and what has to be true before it opens — instead of being spelled
+// out as another hand-built hotspot.
+//
+// A connection stays machine-readable: the generated hotspot is named
+// ExitName(To), so the location graph can be read straight back out of the
+// registered scenes.
+type Exit struct {
+	// To is the scene the exit leads to. Empty means "back the way you came" —
+	// for a scene reachable from several others, where the way out is a
+	// direction rather than a place.
+	To string
+
+	// Label is what the status line calls it.
+	Label string
+
+	// Side places the exit when Area is nil.
+	Side ExitSide
+
+	// Area overrides the edge strip Side would give it.
+	Area Shape
+
+	// Needs is a flag that has to be set before the exit opens; Blocked is
+	// what happens while it is not. The exit is visible either way — a locked
+	// door still says it is a door.
+	Needs   string
+	Blocked Action
+
+	// OnLook and OnTake override Game.ExitLook and Game.ExitTake for this one
+	// exit.
+	OnLook Action
+	OnTake Action
+}
+
+// ExitName is the hotspot name generated for an exit to the named scene.
+func ExitName(to string) string {
+	if to == "" {
+		return "exit:back"
+	}
+	return "exit:" + to
+}
+
+func (e Exit) hotspot(g *Game) Hotspot {
+	var travel Action = GoTo(e.To)
+	if e.To == "" {
+		travel = Back()
+	}
+	if e.Needs != "" {
+		if e.Blocked != nil {
+			travel = If(Flag(e.Needs), travel, e.Blocked)
+		} else {
+			travel = If(Flag(e.Needs), travel)
+		}
+	}
+	area := e.Area
+	if area == nil {
+		area = e.Side.area(g.SceneArea())
+	}
+	look, take := e.OnLook, e.OnTake
+	if look == nil && g.ExitLook != nil {
+		look = g.ExitLook(e)
+	}
+	if take == nil && g.ExitTake != nil {
+		take = g.ExitTake(e)
+	}
+	return Hotspot{
+		Name:   ExitName(e.To),
+		Label:  e.Label,
+		Area:   area,
+		Cursor: CursorExit,
+		OnLook: look,
+		OnUse:  travel,
+		OnTake: take,
+	}
+}
+
+// The edge strips, as fractions of the scene area, so a game that hands over
+// only part of the window to the picture (a HUD along the foot, letterbox
+// bars) gets strips that sit inside the picture rather than under the HUD.
+const (
+	exitEdgeWidth  = 0.0875
+	exitEdgeInset  = 0.080
+	exitEdgeHeight = 0.876
+	exitDoorWidth  = 0.275
+	exitBackInset  = 0.033
+	exitBackHeight = 0.347
+	exitNearHeight = 0.198
+)
+
+func (s ExitSide) area(r Rectangle) Shape {
+	edge := r.W * exitEdgeWidth
+	door := r.W * exitDoorWidth
+	doorX := r.X + (r.W-door)/2
+	switch s {
+	case ExitLeft:
+		return Rect(r.X, r.Y+r.H*exitEdgeInset, edge, r.H*exitEdgeHeight)
+	case ExitRight:
+		return Rect(r.X+r.W-edge, r.Y+r.H*exitEdgeInset, edge, r.H*exitEdgeHeight)
+	case ExitBack:
+		return Rect(doorX, r.Y+r.H*exitBackInset, door, r.H*exitBackHeight)
+	default:
+		return Rect(doorX, r.Y+r.H*(1-exitNearHeight), door, r.H*exitNearHeight)
+	}
+}

state.save.go

@@ -18,6 +18,7 @@ type saveFile struct {
 	Version       int                  `json:"version"`
 	Title         string               `json:"title"`
 	CurrentScene  string               `json:"current_scene"`
+	PreviousScene string               `json:"previous_scene"`
 	SelectedVerb  string               `json:"selected_verb"`
 	ActiveTheme   string               `json:"active_theme"`
 	Characters    map[string]savedChar `json:"characters"`
@@ -98,6 +99,7 @@ func (g *Game) buildSave() saveFile {
 		Version:       saveVersion,
 		Title:         g.Title,
 		CurrentScene:  g.currentScene,
+		PreviousScene: g.previousScene,
 		SelectedVerb:  g.selectedVerb,
 		ActiveTheme:   g.activeTheme,
 		Characters:    make(map[string]savedChar, len(g.chars)),
@@ -142,6 +144,7 @@ func (g *Game) applySave(sf *saveFile) error {
 	g.flashTimer = 0
 
 	g.currentScene = sf.CurrentScene
+	g.previousScene = sf.PreviousScene
 	if sf.SelectedVerb != "" {
 		g.selectedVerb = sf.SelectedVerb
 	}

ui.hotspot_debug.go

@@ -36,8 +36,7 @@ func (h *HotspotDebug) Draw(dst *ebiten.Image, ctx *UICtx) {
 		return
 	}
 	col := g.Theme().HotspotOutline
-	s := g.SceneManager.MustGet(g.currentScene)
+	for _, hs := range g.SceneHotspots(g.currentScene) {
-	for _, hs := range s.Hotspots {
 		b := hs.Area.Bounds()
 		vector.StrokeRect(dst, float32(b.X), float32(b.Y), float32(b.W), float32(b.H), 1, col, false)
 		if hs.Label != "" {

ui.manager.go

@@ -7,20 +7,13 @@ type UIManager = Manager[Widget]
 // order — used by the engine for top-down input dispatch (the widget
 // drawn on top gets the click first).
 func reversedWidgets(m *UIManager) []Widget {
-	names := m.Names()
+	all := m.All()
-	out := make([]Widget, len(names))
+	out := make([]Widget, len(all))
-	for i, n := range names {
+	for i, w := range all {
-		out[len(names)-1-i] = m.MustGet(n)
+		out[len(all)-1-i] = w
 	}
 	return out
 }
 
 // orderedWidgets iterates in registration order — bottom-up draw.
-func orderedWidgets(m *UIManager) []Widget {
+func orderedWidgets(m *UIManager) []Widget { return m.All() }
-	names := m.Names()
-	out := make([]Widget, len(names))
-	for i, n := range names {
-		out[i] = m.MustGet(n)
-	}
-	return out
-}