Robot instructions

Imagine a robot on a grid. It understands exactly four commands and nothing else:

• FORWARD n — move n squares ahead
• LEFT — turn 90° left, staying put
• RIGHT — turn 90° right, staying put
• PICK — pick up whatever is on this square

That's the entire language. "Go to the treasure" means nothing to it. "Head towards the door" means nothing. You must build everything you want out of those four words.

The mistake almost everyone makes on their first try: forgetting that LEFT and RIGHT don't change the robot's square. They only change which way it faces.

So to go from facing north to moving east by two squares, you need two commands: RIGHT then FORWARD 2. Write only FORWARD 2 and the robot cheerfully goes north instead — doing exactly what you said, and not at all what you meant.

The robot starts at the bottom-left of a 4×4 grid, facing north. The treasure sits two squares up and three squares right.

Four commands. Notice that RIGHT costs a line but moves nothing.