The code isn't directly available to students because some teachers might prefer to keep it hidden. You can see the code in your teacher area on the right hand side of the example level (Bubble 2). Just pull out the blue tray on the right and click "Example Solution" and it will take you to a Game Lab project where you can see all the code. You can either share the link with your students or remix the project, edit as you see fit, and share your remixed version.
I would like you straight to the example solution, but because this is an open forum, I can't share it. If you still can't find it, just direct message me and I will send it to you.