I had some difficulty with the Alert (GUI) where it says something and when I click on the button it doesn’t go away, like the game froze, but I can still move around. If anyone can find a solution then I’m all ears.
If the block is destroyed when the message appears then it breaks the game. This happened with “Evil Gameboy”, one of my games. 
Well, the block never got destroyed, I just made it so at the beginning of the level it would say something, but at random times it wouldn’t work when I clicked on the button. I went in and redid all of the speech and it worked temporarily, but then it stopped working again.
Hrmm… @grazer
You can play my game and tell me if the game works or not
http://flowlab.io/game/play/1114643
This has happened to me before, but I have no idea how to fix it.
Mine was later in the game, so I just ignore it and work on something else.
I just made a new one and it works now.
AFTER testing the new one, delete the old one
I redid all of the speech, but It still freezes up. Also, the speech is kind of important to the game. I could try to redo it.