Rover checks the tile ahead before every visit. Predict where it stops, count both successful moves and sensor checks, then inspect the real trace.
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Complete all 4 required tasks with a correct prediction, an inspected trace and an explanation that shows the concept. At least 3 must be independent checks, without answer-level help.
Rover is carrying a parcel east. Keep moving while the next tile is open; the wall marks the safe stopping point.
While rule: A qualifying program uses one while front_is_clear(): loop with an action-only indented body that includes a move. Before each body visit, the condition reads the tile directly ahead. A false first check skips the body; a safety run limit is an emergency guard, not the normal way this loop stops.
1
Predict before RunUse one-based column and row labels. Sensor checks are not moves: include the final false check.
2
Write the sensor loopIndent each robot action under the while line.
Allowed:while front_is_clear():, indented move(), turn_left(), turn_right(), comments and blank lines.
The condition is checked before the body each time. The loop can run zero times when the first check is false. A collision or run limit is not the intended stopping rule.
Allowed Python syntax
For a qualifying puzzle program, use exactly one top-level while front_is_clear(): with one or more indented robot actions. The bounded runner may accept other action-only experiments, but they do not earn this check. No counted for loop, conditions inside the body, assignments, counters, or nested loops.
FLOWCHART · INSPECTED PATH
Run an allowed program to reveal its flowchart. Predict first; then inspect every check and action.
Flowchart
✓ Inspected path◆ Current step
Read or sketch this loop
A rounded shape starts or ends the program. A diamond asks Front is clear? at the robot’s current position and heading. TRUE enters the rectangle actions, in order; the back arrow returns to a fresh sensor check. FALSE leaves the loop. If the first check is FALSE, the body runs zero times.
Unlike for i in range(n), this loop has no fixed visit count. The body must change what the sensor sees so the loop can eventually stop. A safety limit stops experiments that keep repeating; that is a warning, not a normal FALSE exit.
On paper, draw Start → diamond. Label TRUE → body → back to diamond; label FALSE → End. Note the robot’s position and heading at each check. Keep the sketch beside you; no upload is needed. Tiny robot hats remain optional.
Run an allowed program to draw its sensor loop here.
MAP · FULL ROUTE
Predict Rover’s route
1, 3 · E
············→··★■···················
Start: column 1, row 3, facing E. Rover now: column 1, row 3, facing E. Goal: column 4, row 3. Walls at column 5, row 3.
Rover arrow★ goal■ wall
The wall or world edge provides the stopping condition.
4
Explain the stop conditionWhat controls how many times Rover moves? One explanation per completed, fully inspected run.
Help for this sensor puzzleHints build in steps. Worked help requires a deliberate choice.⌄
Highest help used on this case in this session: none