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Tutorial · Grade 11. The Straight Run

Guide the robot to the exit tile and stay there for 3 ticks.

Scenario

The corridor is straight, but the robot has no rules and doesn't know what to do.

Problem statement

Welcome to CTRL!

A robot stands at the entrance of a straight corridor, facing toward the exit. Although it has motors to step forward and wait, its brain has zero rules—so it just stands still.

Your task is to teach it two basic decisions: move forward when the path ahead is clear, and stop once it reaches the exit goal.

The robot relies on you to make decisions. Every tick, the engine reads sensory inputs, finds the first matching rule, and performs its action.

To complete this level, add a rule to step forward when the path is clear, and place a rule to hold at the top so it stops upon reaching the exit.

What this teaches

Understand how rules link a condition (WHEN) to an action (DO), and how rules are evaluated top-to-bottom.

Scroll down to build and test your solution.

Active controller

Apply & Run executes only the selected controller.

How a rule works

A rule has two parts:

WHEN <something is true> → DO <this action>

  • WHEN is a question about what is happening right now. For example: "Is it raining?" or "Is there a wall ahead?"
  • DO is what happens when the answer is yes.
  • The simulation runs one step at a time.
  • On each step, the rules are checked from top to bottom.
  • The first rule that is true wins. The rules below it are skipped for that step.
  • To change which rule wins, move it up or down the list.
  • If no rule is true, nothing happens on that step.
  • Some actions have more than one step, like "turn right, then move". You build these in the Functions tab.
  • Once a multi-step action starts, it finishes all its steps before the rules are checked again. It only stops early if the next step is not safe.
See an example

Two rules for deciding about an umbrella:

1  WHEN isRaining  → take an umbrella
2  WHEN always     → leave the umbrella at home
  • It is raining. Rule 1 is true, so you take an umbrella. Rule 2 is skipped.
  • It is sunny. Rule 1 is false, so rule 2 is checked next. Rule 2 is always true, so you leave the umbrella at home.
  • Order matters. If rule 2 were on top, it would be true every day, and you would never take an umbrella.

Rule folders

Categorise cards without changing their global execution order.

No rules yet. Nothing will happen until you add at least one rule.