Debug the Drawing — Puzzle Cards

Print these and lay them out (or project one at a time) as students arrive on Day 3. Each card shows a goal and the robot’s program drawn as a list of moves. One step is wrong. Teams find the wrong step and trace where the robot actually ends up.

The rule of the game: the robot does the drawing exactly — not what you meant. Read it literally, like a sensor would. One small early mistake throws off everything after it. (That’s the whole reason today’s robot gets a gyro.)

How to read the moves:

  • ↑ Forward N — drive straight N squares in the direction the robot faces
  • ↻ Turn right / ↺ Turn left — spin 90° in place (the robot now faces a new way)
  • The robot starts at S, facing up (↑)

Card 1 — Make a Square (easy)

Goal: Drive a square loop and come back to S, facing up — just like you started.

The robot’s program:

  1. ↑ Forward 3
  2. ↻ Turn right
  3. Forward 3
  4. ↻ Turn right
  5. Forward 3
  6. ↺ Turn LEFT
  7. Forward 3

Trace it on the grid. Where does the robot really end up?

.  .  .  .  .  .
.  .  .  .  .  .
.  .  .  .  .  .
.  .  .  .  .  .
S  .  .  .  .  .

Card 2 — Reach the Flag (early-error)

Goal: Stop on the flag (F).

The robot’s program:

  1. ↑ Forward 3
  2. ↻ Turn right
  3. Forward 3

Trace it. The flag is way up top — does the robot get there?

.  .  .  F  .  .
.  .  .  .  .  .
.  .  .  .  .  .
.  .  .  .  .  .
.  .  .  .  .  .
S  .  .  .  .  .

Card 3 — Turn the Corner (angle bug — gyro theme)

Goal: Drive up, make a clean square corner, then drive straight to the parking spot P (an “L” shape).

The robot’s program:

  1. ↑ Forward 3
  2. ↻ Turn right 45°
  3. Forward 3

Trace it. A turn that isn’t a full 90° — where does leg 2 point now?

.  .  .  .  .  .
.  .  .  .  .  .
.  .  .  .  .  .
.  .  .  P  .  .   ← P is straight to the right of the corner
.  .  .  .  .  .
S  .  .  .  .  .

Card 4 — Around the Block (spot the bug — harder)

Goal: Weave around the wall (▒) and stop on P.

The robot’s program:

  1. ↑ Forward 2
  2. ↻ Turn right
  3. Forward 2
  4. ↺ Turn left
  5. Forward 2
  6. ↺ Turn LEFT
  7. Forward 2

Trace it. One turn in the middle is wrong — which one, and where does it leave the robot?

.  .  .  .  P  .
.  .  ▒  .  .  .
.  .  ▒  .  .  .
.  .  .  .  .  .
S  .  .  .  .  .

Answer Key (instructor only — do not print for students)

Card 1 — Make a Square. The bug is step 6: it turns LEFT instead of right. Steps 1–5 draw three sides of the square (up, across the top, back down). To close the loop the robot must turn right to head back along the bottom toward S. Turning left instead sends it driving away to the right, so it finishes one square-width past the start and never closes the loop. One wrong turn, and the whole last leg is off.

Card 2 — Reach the Flag. The bug is step 1: Forward 3 should be Forward 5 (the flag is 5 squares up). Because the error is in the very first move, everything after it is shifted: the robot turns and drives right at the wrong height and stops two rows below the flag. A small mistake at the start throws off every step after it — the lesson of the day.

Card 3 — Turn the Corner. The bug is step 2: Turn right 45° should be Turn right 90°. With only a half-turn, the robot heads off diagonally instead of straight right, so leg 2 drifts up and away and misses P entirely. Angles have to be exact — this is exactly what the gyro helps the robot get right.

Card 4 — Around the Block. The bug is step 4: Turn left should be Turn right. The robot needs to go up, step right around the wall, then continue up to P. Turning right at step 2 (correct) faces it right; step 4 should turn it back to face up to clear the wall — that’s a right turn. Turning left instead faces it back down/left, and it drives away from the wall and P. Find the early wrong turn and the rest of the path explains itself.

Running it

  • Keep all four out so early arrivals can do more than one (Card 1 → 4 rises in difficulty).
  • Make your own in seconds: draw any correct path, then change one step — flip a turn direction, shorten a forward, or make a turn less than 90°.
  • Land the point out loud before the mission huddle: “The robot did the drawing exactly. One small early slip moved everything after it. Today’s gyro is how we stop that from happening.”