Oh, that is the end of the game, it should force a restart after the player falls off screen. I will look into what's causing that.
To clarify the small crystals are only used to unlock the gates and you don't need more than 4 to complete the game.
But as long as you are enjoying the game that is all that makes me happy. Do let me know if the end of game freeze still happens, remember to redownload the latest version in case you haven't already.