Better flip logic, visuals improvement, and also advanced level section

featuring Aaron's modifier tutorial

Merge pull request #80 from aschrab/multiple_parents

src/js/level/sandbox.js

@@ -319,6 +319,7 @@ var Sandbox = Backbone.View.extend({
           deferred: whenLevelOpen,
           command: command
         });
+        this.hide();
 
         whenLevelOpen.promise.then(function() {
           command.finishWith(deferred);