Suggestions for an education programming project

[Eric]

Hi,

I've been trying to get my son interested in learning some simple
programming for a while. While I understand that a structured tutorial
is best, I think if we can write something cool at least once, it will
encourage him to learn more. While I have a lot of experience with
MATLAB, I've just started playing with Python. It seems to me to be a
great language to learn with. My son has an idea for a program to
write. Basically he would like to present a window with a small circle
on it. The window title would have the instruction to click on the
circle. As the mouse approaches the circle, it moves away from the
spot. Being a kid, the visual and interactive aspect appeals. I think
this will be nice as he can add complexity incrementally such as what
direction to move, how to handle running into the edge of the window,
etc.

What I'd like is a suggestion as to what GUI framework to use (Tk, wx
or something else). I can add modules if necessary. I'd just as soon
use something clean, understandable and not too complex. Certainly,
what ever we use needs to have good documentation. No code please,
that's for us to figure out. In case it matters, we are using are
programming in OS X.

Thanks in advance,

Eric