Session 10 — Escape the Maze

Duration: 60 min · Format: live online

Session goal: by the end, students have built a playable maze game — a player they steer with the arrow keys, walls they cannot walk through, and a goal that says "You win!" and stops the game.

Soft skill focus — Teamwork

Today's human skill: Teamwork. The fastest way to find out if a maze is fair is to let someone else try to escape it.

• Build it in class: once mazes work, pair students up to swap projects and playtest each other's maze — each gives "two stars and a wish" (two things they liked, one idea to make it better). Insist on kind, specific notes.
• Reflection (wrap-up): ask "What did playing a partner's maze teach you about your own?"

Before class — prep

• Open Scratch in a tab (signed in so you can save) and be ready to screen-share the editor.
• Paint a simple maze backdrop ahead of time: Stage → Backdrops → paint thick walls all in one bold colour (e.g. blue). Leave a clear path from a start corner to a goal corner.
• Add a small Player sprite (a ball or dot) and a Goal sprite (a star or flag) at the end of the path. Delete the cat.
• Have the diagram below open to share.

Hook

Ask the class (chat or unmute):

• "In a maze game, what stops you from just walking straight through the walls to the exit?"

Take two answers. Then reveal: "Today we build Escape the Maze. You'll steer a player with the arrow keys — but the moment you touch a wall, the game pushes you back, so the only way out is the real path. Reach the goal and it shouts 'You win!'"

Teach — The plan: backdrop, player, walls, goal

Share this diagram and point to each part as you name it:

Explain the plan — a maze game is a small pile of familiar rules:

• A backdrop with walls all painted in one colour (say blue). The colour is what our code will "feel."
• A Player sprite you steer with the arrow keys (just like the basket last week).
• A Goal sprite at the end of the path.
• Two rules we'll build on the Player:
• 1 · Walls block you — if touching color [blue]? then undo the move you just made, so you can't pass.
• 2 · You win — if touching [Goal]? then say "You win!" and stop [all].

Ask: "Why must every wall be the same colour?" (Because one touching color? block can only check one colour at a time.)

Teach — The "bounce off the wall" trick

Explain: the clever idea is that a wall doesn't have to stop you — it just has to push you back. If a move lands you in a wall, we immediately take a step the opposite way, so you never actually get through. Build the "up arrow" rule live on the Player sprite while they watch.

Build this together (on the Player):

1. From Events, add when green flag clicked, then send the player to the start: go to x: (-200) y: (-150) (adjust to your start corner).

2. Add a forever loop.

3. Inside it, add if <key [up arrow] pressed?> then. Inside that put change y by (5) to step up, then another if right under it: if <touching color [blue]?> then → change y by (-5) — that second block undoes the step if we hit a wall.

Your Player script so far reads:

when green flag clicked
go to x: -200 y: -150
forever
  if key [up arrow] pressed? then
    change y by 5
    if touching color [blue]? then
      change y by -5

Press the green flag and hold up into a wall — the player presses against it but can't pass. That's the whole trick: move, then undo if we're in a wall.

⚠ Watch for the wrong colour: the touching color? block only works if the colour in the block exactly matches your wall paint. Click the colour swatch in the block, use the eyedropper, and click right on a wall to grab the exact colour. A near-miss colour means walls do nothing.

Ask: "The up rule moves +5 then checks the wall. If we hit a wall, what block sends us back?" (change y by -5 — the opposite step.)

Activity — Build the maze game step by step

Students build the whole game. You've done the up arrow together; now they add the other three directions and the win rule. Demo each step, then let them work and circulate.

Part A — set up (do together):

1. If they don't have it: Stage → Backdrops → paint a maze with thick one-colour walls and a clear path. Add a small Player sprite at the start and a Goal sprite at the end. Delete the cat.
2. On the Player, build the start blocks: when green flag clicked → go to x: -200 y: -150 → forever.

Part B — steer with all four arrows (inside the forever loop):

1. Add the up rule from the Teach: if key [up arrow] pressed? then → change y by 5 → if touching color [blue]? then → change y by -5.
2. Right-click that whole if block and duplicate it three times. Change each copy to make down, right, and left:

The four steering rules read:

if key [up arrow] pressed? then
  change y by 5
  if touching color [blue]? then
    change y by -5
if key [down arrow] pressed? then
  change y by -5
  if touching color [blue]? then
    change y by 5
if key [right arrow] pressed? then
  change x by 5
  if touching color [blue]? then
    change x by -5
if key [left arrow] pressed? then
  change x by -5
  if touching color [blue]? then
    change x by 5

1. Press the green flag and drive around — you can follow the path but the walls block you on every side.

Part C — reach the goal and win (inside the same forever loop, below the arrows):

1. Still inside the forever, add one more if <> then. In its hexagon drop Sensing → touching [Goal]?.
2. Inside it, add Looks → say [You win!] for (2) seconds, then Control → stop [all] to end the game.

The finished Player script reads:

when green flag clicked
go to x: -200 y: -150
forever
  if key [up arrow] pressed? then
    change y by 5
    if touching color [blue]? then
      change y by -5
  if key [down arrow] pressed? then
    change y by -5
    if touching color [blue]? then
      change y by 5
  if key [right arrow] pressed? then
    change x by 5
    if touching color [blue]? then
      change x by -5
  if key [left arrow] pressed? then
    change x by -5
    if touching color [blue]? then
      change x by 5
  if touching [Goal]? then
    say [You win!] for 2 seconds
    stop all

1. Press the green flag and play! Steer from the start to the goal — touch it and the game says "You win!" and stops.
2. Make it yours: shrink the player (set size to 60 %) so it fits tighter paths, paint a harder maze, or add a play sound [Cheer] before the win message.

Circulate and ask: "Show me the block that stops you passing a wall. What colour did you eyedrop?"

Debrief: ask 2–3 students to share their screen and race their maze for the class.

Check for understanding

Ask these aloud or in the chat. Answer key (for you):

1. How does a wall stop the player if touching color? can't actually block movement? → We move, then if touching color [wall]? we take the opposite step to undo it — so the player never ends up inside a wall.
2. Why must all the walls be one colour? → touching color? checks a single colour; walls of mixed colours would let the player pass through the ones we didn't check.
3. Which block ends the game when you reach the goal? → stop [all] (Control), inside the if touching [Goal]? rule, after the "You win!" message.

Wrap-up + homework

• Ask one student to explain, in one sentence, the "move then undo" trick for walls.
• Homework — Design a harder maze: repaint the backdrop with a longer, twistier path (same wall colour!), and add a say [You win!] message in your own words. Save and screenshot it for your portfolio.

Teaching notes

• Correct this misconception: "the wall pushes the player back on its own." The backdrop is just a picture — it has no code. Our if touching color? rule does the pushing by undoing the step. If the player walks through walls, that undo if is missing or the colour is wrong.
• Fast finishers (extension): add a coin sprite the player must grab first (if touching [Coin]? then hide → change [score] by 1), or a timer that ends the game with "Too slow!" using stop [all]. Or add a trap colour (red) that sends the player back to the start with go to x: -200 y: -150.
• Low-tech fallback: no devices? Draw a maze on paper or tape one on the floor. A child is the player and may only move along open squares; a partner is the rule who calls "wall!" and makes them step back whenever they touch a line. Reaching the goal square wins. The idea — walls are a rule, not magic — is the lesson.

Vocabulary

Resources

• Scratch editor — where students build (free, in the browser).
• Scratch Ideas — Make It Fly / Maze starter cards — official starter cards, including maze-style movement.
• Scratch Coding Cards (PDF) — printable recipes including "touching color" wall detection.

Practice set

Extra tasks to sharpen the maze game. Work them easy → hard, at lab time or for homework. Answers follow each arrow.

1. Colour clue. Which block family holds touching color? and touching [Goal]?? → Sensing (cyan).

2. Predict. The player has change y by 5 for the up arrow but no if touching color [blue]? check after it. What happens? → The player walks straight through walls — nothing pushes it back.

3. Direction. For the right arrow you move change x by 5. If that lands you in a wall, which block undoes it? → change x by -5 (the opposite step).

4. Fix it (spot the bug). A student's walls don't stop the player, even though the touching color? blocks are there. What's the likely cause? → The colour in the block doesn't match the wall paint. Fix: click the colour swatch, use the eyedropper, and click directly on a wall.

5. Make it (build task). Add a rule so touching the goal plays a sound before the win message. → Inside if touching [Goal]? then, add Sound → play sound [Cheer] before say [You win!] for 2 seconds.

6. Two rules (harder). Write the pseudo-code for a trap rule: if the player touches red, send it back to the start. → if touching color [red]? then → go to x: -200 y: -150.

Going deeper (optional)

Optional — for a class with a working maze that wants to understand collision.

Why "move then undo" beats "check then move." We could try to look ahead before moving, but that's hard — Scratch can't easily "peek" one step forward. Moving first and undoing if we're in a wall is simpler and always correct: the player may flicker at a wall for a frame, but never gets stuck inside it. Many real games use this same "move, test, resolve" pattern every frame.

Colour collision vs sprite collision. We used two kinds of sensing today: touching color? for the walls (a painted backdrop) and touching [Goal]? for the goal (a whole sprite). Point out the choice — walls are part of the picture, so we sense the colour; the goal is its own object, so we sense the sprite. Picking the right sensing block for the right thing is a real design decision.

Common mistakes & fixes

• Mistake: The wall colour in touching color? doesn't match the paint, so walls do nothing. → Fix: use the eyedropper in the colour swatch and click right on a wall.
• Mistake: Walls are painted in several colours. → Fix: repaint every wall in one colour so a single touching color? catches them all.
• Mistake: The undo block moves the same way as the step (e.g. +5 then +5), flinging the player deeper into the wall. → Fix: the undo must be the opposite sign of the move.
• Mistake: The win rule uses stop [this script] (or nothing), so the game keeps running after "You win!". → Fix: use stop [all] to end everything.
• Mistake: The steering if blocks sit outside the forever loop, so the player moves once or not at all. → Fix: put all four arrow rules and the goal rule inside the forever.

Next session

Session 11 — Tell an Animated Story: students switch from games to storytelling — using costumes, say, wait and broadcast to make two sprites talk, take turns and act out a scene.