Demo fix

Scenes/VirtualChemDemo.cs

@@ -7,6 +7,11 @@ public partial class VirtualChemDemo : Node2D
 	public Bottle SelectedBottle { get; set; }
 	private StringLoader ExpressionLoader { get; set; }
 
+	public void PopupStringLoader()
+	{
+		ExpressionLoader.Visible = true;
+	}
+
 	public void OneStep()
 	{
 		Flask.Content.OneStep();
@@ -21,6 +26,7 @@ public partial class VirtualChemDemo : Node2D
 		FullRepr = GetNode<RichTextLabel>("HRepr/FullRepr");
 		Flask = GetNode<Flask>("Flask");
 		GlobalScene.Demo = this;
+		
 	}
 
 	// Called every frame. 'delta' is the elapsed time since the previous frame.