How to make a sprite move around in a specific area.

SUBJECT: How do I make the sprite move around in a certain area, not the whole screen

I am new to app inventor, and I would like to make an app that does the following.  I kindly ask for your help and prompt response, as this is for a class and the project is due in 5 days.

OVERVIEW OF APP:

My app will be a flicking a hockey puck into a goal. But you have to get the puck past the moving goalie.

ISSUE(S) I NEED HELP WITH:

1.        The issue that I am struggling with is identifying how do I get the goalie moving only in the goal, not the whole screen. 

I have attached my project to date. 

FinalProject.aia

If you are asking for help, I recommend you to make it as easy for others to be able to help you ... You probably will get more feedback then...

which means in your case post a screenshot of your relevant blocks and probably a drawing of how you like to move the goalie...

apk files are not allowed, see also the posting guidelines!

Make some thin line Sprites to act as walls around the goal box.

Have the goalie bounce off them.