Rover arrives at small corridors that may be open or blocked. Use one sensor choice and a while loop to deliver on varied maps, then test a layout that exposes the rule’s limit.
What’s saved:Code, plans and predictions clear when you leave or reload. If you turn saving on, only which challenges you finished and how much help you used is kept on this device. Test accounts also share it, and lesson timing, with the site’s maintainer.
◇ Your mastery goalCombined control
Complete all 4 required tasks with a correct prediction, an inspected trace and an explanation that shows the concept. At least 1 must be independent checks, without answer-level help.
At an open gate, follow the corridor. At a blocked gate, turn right and follow the other corridor.
0 / 4 maps checked
Your job: Use the first sensor result to choose a branch, then use a while loop to continue safely along that branch.
Count carefully: successful moves change the pose. IF and WHILE sensor checks read the tile before a branch or loop body; checks do not add moves. FOR visit markers are not sensor checks. A run safety limit is an emergency stop, not the normal way a sensor loop finishes.
Rover must travel east through 2 open tiles and stop at the wall.
2
Predict before RunUse one-based column and row. Include the final false check when a while loop stops.
3
Write the control programUse the lesson’s bounded Python control syntax.
Allowed subset:move(), turns, if/else front_is_clear(), for i in range(n) and while front_is_clear(). Loops and branches contain fixed robot actions or supported nested control.
Syntax and safety guide
Only the supported, bounded grammar runs in the isolated lesson runner. The parser validates untaken branches too. No variables, imports, arbitrary Python or goal-search helper is available. A 128-event safety limit stops runaway experiments; a sensor loop should normally exit on a false check.
FLOWCHART · INSPECTED PATH
Run a checked program to see its real control path.
Flowchart
✓ Inspected path◆ Current step
Read or sketch this program
Start and End are rounded. Rectangles are actions. For IF, follow the TRUE or FALSE branch and merge afterward. WHILE checks before every whole body visit; TRUE runs the body and returns to a fresh check, FALSE leaves it. FOR repeats the whole body its range count, including zero visits.
Draw the same shapes and labelled arrows on paper before coding. Trace position and heading after every action. A sensor checks only at its own diamond: two moves in one body are not two checks. A safety limit or collision stops an experiment without normal End.
Highlights and ✓ counts show only inspected events. Counted-loop arrows explain order; no extra counter or exit events are invented. Your sketch stays with you; no upload is needed.
Run an allowed program to draw its chart.
MAP · CURRENT POSE
Predict Rover’s route
1, 1 · E
→·★■································
Start: column 1, row 1, facing E. Rover now: column 1, row 1, facing E. Goal: column 3, row 1. Walls at column 4, row 1.
Walls are listed by one-based column and row.
Evidence still neededUse the same algorithm across the required maps. Keep each prediction and trace attached to that version.
Contextual HelpHints build one step at a time; answer-level help is a deliberate choice.⌄
Highest help on this map and stage: none
For Further Reading and Exploration
These are outside sites with their own rules. You will see a notice before you leave. Pick one, not all.
Automate the Boring Stuff with Python
Free book to read online. Short, useful programs show how real scripts mix decisions and loops.
Hands-on
May need an install
Ask an adult
CS50's Introduction to Programming with Python
Free Harvard course with videos and notes. Problem sets let you practice mixing conditionals and loops in small programs.
Hands-on
Advanced
May count visits
draw.io diagram maker
Draw your delivery route plan as a flowchart before you code. Seeing the plan helps you spot missing steps. Save on your device.
Hands-on
Raspberry Pi Foundation Projects
Step-by-step Python projects. Pick one that mixes choices and repeats. Some need hardware, so check the parts list first.