diff --git a/src/classes/communication.gd b/src/classes/communication.gd
index 8198203..7cfb94a 100644
--- a/src/classes/communication.gd
+++ b/src/classes/communication.gd
@@ -28,7 +28,8 @@ var presenloader: Node
 # Presentation data
 var entrypoint: PresencodeEntrypoint
 var manifest: Dictionary
-var current_slide: int = -1
+var current_slide: int = 0
+var slide_switch_in_progress: bool = false
 
 # +++ initialization +++
 func _init(core_new: Core, presenloader_new: Node) -> void:
@@ -56,13 +57,17 @@ func _process(_delta: float) -> void:
 
 # +++ slide management +++
 func switch_slide(new_slide: int) -> PresencodeTypes.PresencodeError:
+	if slide_switch_in_progress: return PresencodeTypes.PresencodeError.ALREADY_RUNNING
+	slide_switch_in_progress = true
 	var old_slide: int = current_slide
 	
 	if new_slide < 0:
 		logger.error(core.misc.stringify_variables("Invalid slide %slide%", { "slide": new_slide }))
+		slide_switch_in_progress = false
 		return PresencodeTypes.PresencodeError.INVALID_SLIDE
 	if new_slide > manifest["slides"]:
 		logger.error(core.misc.stringify_variables("Invalid slide %slide%", { "slide": new_slide }))
+		slide_switch_in_progress = false
 		return PresencodeTypes.PresencodeError.INVALID_SLIDE
 	
 	logger.info(core.misc.stringify_variables("Switching from slide %old% to %new%", { "old": old_slide, "new": new_slide }))
@@ -74,13 +79,16 @@ func switch_slide(new_slide: int) -> PresencodeTypes.PresencodeError:
 	
 	# Call switch_slide()
 	logger.verb("Switching slide")
-	await entrypoint.switch_slide(new_slide)
+	await entrypoint.switch_to_slide(new_slide)
 	
 	# Play AFTER animation
 	if manifest["animations"]:
 		logger.verb("Starting AFTER animation")
 		await entrypoint.play_animation(PresencodeTypes.AnimationStage.AFTER, old_slide, new_slide)
 	
+	current_slide = new_slide
+	slide_switch_in_progress = false
+	
 	return PresencodeTypes.PresencodeError.OK
 
 func remove_all_slides() -> void:
diff --git a/src/classes/types.gd b/src/classes/types.gd
index 172546b..a9ba969 100644
--- a/src/classes/types.gd
+++ b/src/classes/types.gd
@@ -19,7 +19,8 @@ class_name PresencodeTypes
 
 enum PresencodeError {
 	OK,
-	INVALID_SLIDE
+	INVALID_SLIDE,
+	ALREADY_RUNNING,
 }
 enum AnimationStage { BEFORE, AFTER }
 
@@ -27,4 +28,5 @@ func presencodeerror_string(error: PresencodeError) -> String:
 	match(error):
 		PresencodeError.OK: return "OK"
 		PresencodeError.INVALID_SLIDE: return "Invalid Slide"
+		PresencodeError.ALREADY_RUNNING: return "Already running"
 		_: return "<invalid enum value>"