diff --git a/engine/debug.go b/engine/debug.go
index aaf1e25..6879712 100644
--- a/engine/debug.go
+++ b/engine/debug.go
@@ -18,9 +18,14 @@ func init() {
 }
 
 // PerfDisplay debugprints CurrentTPS and CurrentFPS in the top left.
-type PerfDisplay struct{}
+type PerfDisplay struct {
+	Hidden bool
+}
 
-func (PerfDisplay) Draw(screen *ebiten.Image, _ ebiten.GeoM) {
+func (p PerfDisplay) Draw(screen *ebiten.Image, _ ebiten.GeoM) {
+	if p.Hidden {
+		return
+	}
 	ebitenutil.DebugPrint(screen, fmt.Sprintf("TPS: %0.2f  FPS: %0.2f", ebiten.CurrentTPS(), ebiten.CurrentFPS()))
 }
 
diff --git a/engine/game.go b/engine/game.go
index f2caf65..5f17554 100644
--- a/engine/game.go
+++ b/engine/game.go
@@ -2,6 +2,7 @@ package engine
 
 import (
 	"encoding/gob"
+	"fmt"
 
 	"github.com/hajimehoshi/ebiten/v2"
 )
@@ -10,10 +11,10 @@ func init() {
 	gob.Register(Game{})
 }
 
-// IDer components have a name. This makes it easier for components to
-// find and interact with one another.
-type IDer interface {
-	ID() string
+// Identifier components have a sense of self. This makes it easier for
+// components to find and interact with one another.
+type Identifier interface {
+	Ident() string
 }
 
 // Scanner components can be scanned. It is called when the game
@@ -47,6 +48,20 @@ func (g *Game) Update() error {
 	return g.Scene.Update()
 }
 
+// RegisterComponent tells the game there is a new component.
+func (g *Game) RegisterComponent(c interface{}) {
+	if id, ok := c.(Identifier); ok {
+		g.componentsByID[id.Ident()] = c
+	}
+}
+
+// UnregisterComponent tells the game the component is no more.
+func (g *Game) UnregisterComponent(c interface{}) {
+	if id, ok := c.(Identifier); ok {
+		delete(g.componentsByID, id.Ident())
+	}
+}
+
 // Component returns the component with a given ID.
 func (g *Game) Component(id string) interface{} { return g.componentsByID[id] }
 
@@ -71,12 +86,10 @@ func (g *Game) walk(c interface{}, v func(interface{}) bool) {
 
 // Build builds the component database.
 func (g *Game) Build() {
-	byID := make(map[string]interface{})
-	g.walk(g.Scene, func(c interface{}) bool {
-		if id, ok := c.(IDer); ok {
-			byID[id.ID()] = c
-		}
+	g.componentsByID = make(map[string]interface{})
+	g.Walk(func(c interface{}) bool {
+		g.RegisterComponent(c)
 		return true
 	})
-	g.componentsByID = byID
+	fmt.Printf("%#v\n", g.componentsByID)
 }
diff --git a/engine/z.go b/engine/misc.go
similarity index 52%
rename from engine/z.go
rename to engine/misc.go
index cf34c60..fcc386a 100644
--- a/engine/z.go
+++ b/engine/misc.go
@@ -1,5 +1,11 @@
 package engine
 
+// ID implements Identifier directly (as a string value).
+type ID string
+
+// Ident returns id as a string.
+func (id ID) Ident() string { return string(id) }
+
 // ZPos implements ZPositioner directly (as a float64 value).
 type ZPos float64
 
diff --git a/engine/scene.go b/engine/scene.go
index c1ccb39..57ba004 100644
--- a/engine/scene.go
+++ b/engine/scene.go
@@ -30,11 +30,17 @@ type ZPositioner interface {
 // Scene manages drawing and updating a bunch of components.
 type Scene struct {
 	Components []interface{}
-	Transform  ebiten.GeoM
+	Hidden     bool
+	ID
+	Transform ebiten.GeoM
+	ZPos
 }
 
 // Draw draws all components in order.
 func (s *Scene) Draw(screen *ebiten.Image, geom ebiten.GeoM) {
+	if s.Hidden {
+		return
+	}
 	geom.Concat(s.Transform)
 	for _, i := range s.Components {
 		if d, ok := i.(Drawer); ok {
diff --git a/engine/tiles.go b/engine/tiles.go
index b689707..296e505 100644
--- a/engine/tiles.go
+++ b/engine/tiles.go
@@ -15,6 +15,8 @@ func init() {
 
 // Tilemap renders a grid of tiles.
 type Tilemap struct {
+	Hidden bool
+	ID
 	Map       [][]Tile
 	Src       ImageRef // must be a horizontal tile set
 	TileSize  int
@@ -24,6 +26,9 @@ type Tilemap struct {
 
 // Draw draws the tilemap.
 func (t *Tilemap) Draw(screen *ebiten.Image, geom ebiten.GeoM) {
+	if t.Hidden {
+		return
+	}
 	geom.Concat(t.Transform)
 	for j, row := range t.Map {
 		for i, tile := range row {
diff --git a/main.go b/main.go
index a9ed90a..d84bcb3 100644
--- a/main.go
+++ b/main.go
@@ -74,6 +74,7 @@ func main() {
 		ScreenHeight: screenHeight,
 		ScreenWidth:  screenWidth,
 		Scene: &engine.Scene{
+			ID: "root_scene",
 			Components: []interface{}{
 				&engine.GobDumper{
 					KeyCombo: []ebiten.Key{