Track: Unplugged · Lesson 2 of 10 · Ages: 6+ · Time: 35 minutes
Real robots follow a list of commands, one after another. That list is called a program. Today you will write programs using just three cards, and a friend will act as the robot and follow them.
Beep says I only know three tricks: go forward one square, turn left and turn right. With just those, I can reach any battery on the grid! Beep boop!
What you need
- A grid of squares. Use paper squares or masking tape on the floor, about 5 squares wide and 4 squares tall. Or draw the grid on paper and use a small toy as the robot.
- Paper cards: lots of Forward cards (an arrow pointing up), some Turn Left cards and some Turn Right cards.
- A “battery” to reach, like a coin or a paper square with a battery drawn on it.
- A friend to be the robot.
Safety first Play on a floor that is not slippery, and walk slowly. No running! If the floor is smooth, play on a table with a toy robot instead. Stick paper squares down with tape so they do not slide.
Grown-ups The big idea is a sequence: steps run in order, one at a time, and the robot does exactly what the cards say. Lay the cards in a row on the floor so the child can point at each card while the robot follows. The most common slip is mixing up the robot’s left with the child’s left. Let the robot walk the program, and that mistake sorts itself out.
The three cards
| Card | What the robot does |
|---|---|
| Forward (F) | Walks one square in the way it is facing. |
| Turn Left (L) | Turns on the spot a quarter turn to its own left. It does not move to another square. |
| Turn Right (R) | Turns on the spot a quarter turn to its own right. |
In the pictures below, Forward is a blue card with an up arrow, Turn Left is purple and Turn Right is pink. Use any colours you like for your own cards.
Notice that “left” means the robot’s left, not yours. If the robot is facing you, its left is on your right!
Your first program
Beep starts on the left and faces the right. The battery is three squares ahead. Which cards do you need?
Three Forward cards in a row: F F F. A program like this is a sequence, which means the steps happen one after another in order.
Adding a turn
Now the battery is round a corner. Beep starts in the bottom left corner, facing right.
The program is F F L F F. Beep walks forward twice, turns left so it faces up the page, then walks forward twice more.
Walls in the way
Here is a bigger grid with a wall of three brick blocks. Beep cannot walk through walls.
The program is F L F F F R F F F. Beep takes one step, turns left (now facing up), walks three squares to the top, turns right (now facing along the top) and walks three squares to the battery.
Bugs happen
Now, what if we forget the turns? A program F F F on the same grid sends Beep straight into the wall.
Oops! A mistake in a program is called a bug. When that happens, do not worry. Find the card that is wrong, fix it and try again.
Pixel says Walk the program yourself, one card at a time, with your finger on the map. That is how I find bugs fast. Meow!
How to play
- One player is the programmer. They put the battery somewhere on the grid and put the robot on a start square.
- The programmer lays out cards in a row to make a program.
- The robot player does exactly what the cards say, one at a time. No peeking ahead and no helping!
- Did the robot reach the battery? If yes, swap roles. If not, fix the program.
Challenges
Try it Beep starts at the top left corner, facing down. The battery is at the bottom right. Three blocks are in the way. Write a program with the cards.
Show a hint
Beep faces down. Walk down the left side first, then turn towards the battery.
Show the answer
One answer is F F F L F F F F. Beep walks down three squares to the bottom row, turns left (facing down, its left is the right side of the page) and then walks four squares to the battery.
There are other correct programs too, such as L F F F F R F F F along the top and then down. Both work!
Try it How many Turn Right cards would you need in a row to make the robot face the opposite way?
Show the answer
Two. One turn right is a quarter turn, so two turns right make a half turn and the robot faces the opposite way.
What you learned
- A program is a list of commands. A sequence runs them in order.
- Turn Left and Turn Right turn the robot on the spot, using its left and right.
- A mistake is a bug. You can find it by walking through the program one card at a time.