VISUAL · BLOCKS → PYTHON

The Embodied Loop

Wire a sense->decide->act loop that drives the rover forward and halts it within 0.25 m of the goal with no overshoot.

01Challenge

Bench opens in the Blockly editor. The rover sits at the origin facing an amber goal 3.0 m dead ahead. Make the rover drive forward and stop when it gets close to the goal — not crash through it, not stop early. Drag blocks, press Run. You have not been taught the right answer yet — try it.

02Model

A robot is not a program that runs once. Picture driving to a goal: point it, push go — and it overshoots, because a single command can't know when to stop. So it does something else: it SENSES (how far to the goal?), DECIDES (close enough yet?), and ACTS (drive, or stop) — then does the whole thing again, many times a second. That loop is the robot.

The one thing that trips everyone up: if you check 'am I there yet?' only once, the rover never re-asks and overshoots forever. The deciding has to live inside the loop, asked every single tick.

Sense → think → act, closed around the world.

03Guided practice

Step 1 (worked): the loop and forward-drive block are placed; you drop in if goal distance < ??? with a number near 0.25. Step 2 (faded): rebuild the loop and choose the threshold yourself. Step 3 (independent): tune the threshold so the rover halts within tolerance — too small overshoots, too large stops early.

04Feedback

PASS WHEN Stopped with final goal-distance <= 0.25 m, never exceeding goal x by more than 0.30 m, with the stop-decision evaluated every loop iteration.

FAIL: ran the full 15 s without stopping — no stop condition reached; place a goal-distance read in the comparison.
FAIL: overshot the goal by 0.62 m — the rover never re-checks distance while driving; move the if inside the repeat-forever loop.
FAIL: halted 0.71 m short — stop threshold fires while still far away; lower it toward 0.25 m.

05Retrieve & space

Tag fragments as SENSE / DECIDE / ACT (read_range -> SENSE, set_motor -> ACT, if < 0.25 -> DECIDE).
Predict: change threshold 0.25 -> 0.6 — does the rover stop closer or farther from the goal? (Farther — triggers sooner.)
Spot-the-bug: a block stack has the stop-check outside the loop; drag it back inside.

06Mastery & project

From the fixed seed, the rover drives forward and halts within 0.25 m of the goal with no overshoot beyond 0.30 m, stop-decision provably inside the loop (L0: runs a given loop).

Contributes the stop-on-condition STOP primitive to the capstone; the 'test the sensor every tick, inside the loop' habit is the skeleton of every later controller (PID loop, timer-ISR tick).

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VISUAL · BLOCKS → PYTHON

The Embodied Loop

Drag blocks (shown here as the Python they generate) so the rover senses, decides, and acts every tick.