Hi!
Here is an idea: why don't you build a robot that can figure out how to move where ever you connect his motors!
You have about 10 outputs, and you randomly select two of them(or someone else selects them) and with few accelerometers he could move in any direction you want! After that, you make him a line follower...
You could make a robot thats is a line follower, can color detect and do some other stuff!
Combine these ideas if you want to!
, yann