diff --git a/dev-assets/doodads/on-off/state-block-blue.js b/dev-assets/doodads/on-off/state-block-blue.js
index 0b287e3..f09f5cc 100644
--- a/dev-assets/doodads/on-off/state-block-blue.js
+++ b/dev-assets/doodads/on-off/state-block-blue.js
@@ -7,15 +7,10 @@ function main() {
 
 	Message.Subscribe("broadcast:state-change", function(newState) {
 		state = !newState;
-		console.warn("BLUE BLOCK Received state=%+v, set mine to %+v", newState, state);
 
 		// Layer 0: ON
 		// Layer 1: OFF
-		if (state) {
-			Self.ShowLayer(0);
-		} else {
-			Self.ShowLayer(1);
-		}
+		Self.ShowLayer(state ? 0 : 1);
 	});
 
 	Events.OnCollide(function(e) {
diff --git a/dev-assets/doodads/on-off/state-block-orange.js b/dev-assets/doodads/on-off/state-block-orange.js
index 634d5e8..dfea8b7 100644
--- a/dev-assets/doodads/on-off/state-block-orange.js
+++ b/dev-assets/doodads/on-off/state-block-orange.js
@@ -7,15 +7,10 @@ function main() {
 
 	Message.Subscribe("broadcast:state-change", function(newState) {
 		state = newState;
-		console.warn("ORANGE BLOCK Received state=%+v, set mine to %+v", newState, state);
 
 		// Layer 0: OFF
 		// Layer 1: ON
-		if (state) {
-			Self.ShowLayer(1);
-		} else {
-			Self.ShowLayer(0);
-		}
+		Self.ShowLayer(state ? 1 : 0);
 	});
 
 	Events.OnCollide(function(e) {
diff --git a/dev-assets/doodads/on-off/state-button.js b/dev-assets/doodads/on-off/state-button.js
index 51a2af3..8770b08 100644
--- a/dev-assets/doodads/on-off/state-button.js
+++ b/dev-assets/doodads/on-off/state-button.js
@@ -1,14 +1,22 @@
 // State Block Control Button
+
+// Button is "OFF" by default.
+var state = false;
+
 function main() {
-	console.log("%s initialized!", Self.Doodad.Title);
+	console.log("%s ID '%s' initialized!", Self.Doodad.Title, Self.ID());
 	Self.SetHitbox(0, 0, 33, 33);
 
 	// When the button is activated, don't keep toggling state until we're not
 	// being touched again.
 	var colliding = false;
 
-	// Button is "OFF" by default.
-	var state = false;
+	// If we receive a state change event from a DIFFERENT on/off button, update
+	// ourself to match the state received.
+	Message.Subscribe("broadcast:state-change", function(value) {
+		state = value;
+		showSprite();
+	});
 
 	Events.OnCollide(function(e) {
 		if (colliding) {
@@ -17,24 +25,16 @@ function main() {
 
 		// Only trigger for mobile characters.
 		if (e.Actor.IsMobile()) {
-			console.log("Mobile actor %s touched the on/off button!", e.Actor.Actor.Filename);
-
 			// Only activate if touched from the bottom or sides.
 			if (e.Overlap.Y === 0) {
-				console.log("... but touched the top!");
 				return false;
 			}
 
 			colliding = true;
-			console.log("   -> emit state change");
 			state = !state;
 			Message.Broadcast("broadcast:state-change", state);
 
-			if (state) {
-				Self.ShowLayer(1);
-			} else {
-				Self.ShowLayer(0);
-			}
+			showSprite();
 		}
 
 		// Always a solid button.
@@ -45,3 +45,12 @@ function main() {
 		colliding = false;
 	})
 }
+
+// Update the active layer based on the current button state.
+function showSprite() {
+	if (state) {
+		Self.ShowLayer(1);
+	} else {
+		Self.ShowLayer(0);
+	}
+}
diff --git a/pkg/doodle.go b/pkg/doodle.go
index 7032a5e..b097e53 100644
--- a/pkg/doodle.go
+++ b/pkg/doodle.go
@@ -99,8 +99,6 @@ func (d *Doodle) Run() error {
 
 	// Set up the default scene.
 	if d.Scene == nil {
-		// d.Goto(&GUITestScene{})
-		// d.NewMap()
 		d.Goto(&MainScene{})
 	}
 
diff --git a/pkg/scripting/events.go b/pkg/scripting/events.go
index b6e725e..04eaf9f 100644
--- a/pkg/scripting/events.go
+++ b/pkg/scripting/events.go
@@ -2,6 +2,7 @@ package scripting
 
 import (
 	"errors"
+	"sync"
 
 	"git.kirsle.net/go/render/event"
 	"github.com/robertkrimen/otto"
@@ -25,6 +26,7 @@ var (
 // Events API for Doodad scripts.
 type Events struct {
 	registry map[string][]otto.Value
+	lock     sync.RWMutex
 }
 
 // NewEvents initializes the Events API.
@@ -70,6 +72,9 @@ func (e *Events) register(name string, callback otto.Value) otto.Value {
 		return otto.Value{} // TODO
 	}
 
+	e.lock.Lock()
+	defer e.lock.Unlock()
+
 	if _, ok := e.registry[name]; !ok {
 		e.registry[name] = []otto.Value{}
 	}
@@ -81,6 +86,9 @@ func (e *Events) register(name string, callback otto.Value) otto.Value {
 // Run an event handler. Returns an error only if there was a JavaScript error
 // inside the function. If there are no event handlers, just returns nil.
 func (e *Events) run(name string, args ...interface{}) error {
+	e.lock.RLock()
+	defer e.lock.RUnlock()
+
 	if _, ok := e.registry[name]; !ok {
 		return nil
 	}
diff --git a/pkg/scripting/pubsub.go b/pkg/scripting/pubsub.go
index 407f22e..8324698 100644
--- a/pkg/scripting/pubsub.go
+++ b/pkg/scripting/pubsub.go
@@ -23,7 +23,9 @@ func RegisterPublishHooks(s *Supervisor, vm *VM) {
 	// for any matching messages received.
 	go func() {
 		for msg := range vm.Inbound {
-			log.Warn("vm: %s  msg: %+v", vm.Name, msg)
+			vm.muSubscribe.RLock()
+			defer vm.muSubscribe.RUnlock()
+
 			if _, ok := vm.subscribe[msg.Name]; ok {
 				for _, callback := range vm.subscribe[msg.Name] {
 					callback.Call(otto.Value{}, msg.Args...)
@@ -35,6 +37,9 @@ func RegisterPublishHooks(s *Supervisor, vm *VM) {
 	// Register the Message.Subscribe and Message.Publish functions.
 	vm.vm.Set("Message", map[string]interface{}{
 		"Subscribe": func(name string, callback otto.Value) {
+			vm.muSubscribe.Lock()
+			defer vm.muSubscribe.Unlock()
+
 			if !callback.IsFunction() {
 				log.Error("SUBSCRIBE(%s): callback is not a function", name)
 				return
@@ -57,8 +62,13 @@ func RegisterPublishHooks(s *Supervisor, vm *VM) {
 
 		"Broadcast": func(name string, v ...interface{}) {
 			// Send the message to all actor VMs.
-			for _, vm := range s.scripts {
-				vm.Inbound <- Message{
+			for _, toVM := range s.scripts {
+				if vm.Name == toVM.Name {
+					log.Debug("Broadcast(%s): skip to vm '%s' cuz it is the sender", name, toVM.Name)
+					continue
+				}
+
+				toVM.Inbound <- Message{
 					Name: name,
 					Args: v,
 				}
diff --git a/pkg/scripting/vm.go b/pkg/scripting/vm.go
index 21f78f5..d3cfdef 100644
--- a/pkg/scripting/vm.go
+++ b/pkg/scripting/vm.go
@@ -3,6 +3,7 @@ package scripting
 import (
 	"fmt"
 	"reflect"
+	"sync"
 	"time"
 
 	"git.kirsle.net/apps/doodle/pkg/log"
@@ -25,9 +26,10 @@ type VM struct {
 	// Each VM also has an array of Outbound channels which map to the Inbound
 	//     channel of the VMs it is linked to, for pushing out Message.Publish()
 	//     messages.
-	Inbound   chan Message
-	Outbound  []chan Message
-	subscribe map[string][]otto.Value // Subscribed message handlers by name.
+	Inbound     chan Message
+	Outbound    []chan Message
+	subscribe   map[string][]otto.Value // Subscribed message handlers by name.
+	muSubscribe sync.RWMutex
 
 	vm *otto.Otto
 
diff --git a/pkg/uix/actor_collision.go b/pkg/uix/actor_collision.go
index a2fda38..9a5f867 100644
--- a/pkg/uix/actor_collision.go
+++ b/pkg/uix/actor_collision.go
@@ -103,6 +103,12 @@ func (w *Canvas) loopActorCollision() error {
 	var collidingActors = map[string]string{}
 	for tuple := range collision.BetweenBoxes(boxes) {
 		a, b := w.actors[tuple.A], w.actors[tuple.B]
+
+		// If neither actor is mobile, don't run collision handlers.
+		if !(a.IsMobile() || b.IsMobile()) {
+			continue
+		}
+
 		collidingActors[a.ID()] = b.ID()
 
 		// Call the OnCollide handler for A informing them of B's intersection.
@@ -219,7 +225,7 @@ func (w *Canvas) loopActorCollision() error {
 					InHitbox: info.Overlap.Intersects(a.Hitbox()),
 					Settled:  true,
 				}); err != nil && err != scripting.ErrReturnFalse {
-					log.Error(err.Error())
+					log.Error("VM(%s).RunCollide: %s", a.ID(), err.Error())
 				}
 			}
 		}