diff --git a/evolve-die-repeat/molecular/molecular_player.gd b/evolve-die-repeat/molecular/molecular_player.gd
index d6b6672..732e8c2 100644
--- a/evolve-die-repeat/molecular/molecular_player.gd
+++ b/evolve-die-repeat/molecular/molecular_player.gd
@@ -20,4 +20,15 @@ func _process(delta):
 
 	move_and_collide(speed * velocity * delta)
 	#position += speed * velocity * delta
-	position = position.clamp(Vector2.ZERO, screen_size)
+	position = get_boundaried_position(position)
+	
+	# periodic boundary
+	
+func get_boundaried_position(position):
+	## clamp
+	#return position.clamp(Vector2.ZERO, screen_size)
+	
+	## periodic
+	position.x = wrapf(position.x, 0, screen_size.x)
+	position.y = wrapf(position.y, 0, screen_size.y)
+	return position