For example multiple rectangles on screen, varying in sizes and positions.
I don't really know where to start.
I don't know if there's a way to draw more than one shape on screen rather than writing code for each one, is there an easier way to do this?

Thank you to both, all the ways mentioned were really informative and got the job done. I'm a beginner so I really can't picture it in an abstract way but now I see

It's as simple as it sounds to most of you. I guess I don't get the logic? if x < width then x = x + 1 elseif x > width then x = x - 1 obviously the above is wrong, but I hope you know why I'm stuck from it How can I tell the program to change the direction of the rectangle when it reaches the most ...