Use the arrow keys to move the minisub. Try to collect the crystals and you will see how many crystals you've collected in the top left corner. but, watch out, because when you stop the program (hit the red stop sign) you lose your score.
I used the idea from a lego set that I built and decided to make part of it in scratch. Note that this is for desktops only. for mobile devices go to my other game that is exactly like this one, except you can play it on mobile devices. This is the URL for it. https://scratch.mit.edu/projects/459189427