Goals & Win Conditions — when does the game end?

Learning Goals 3 min

By the end of this lesson you will be able to:

1. Paint a coloured goal square on the backdrop and use touching color [#00ff00] ? as a win trigger.
2. Use a broadcast + switch backdrop + stop [all v] chain to end the game cleanly.
3. Track a multi-stage win with a keys-found list — collect three coloured keys before the goal counts.

Warm-Up — the maze with no finish line 7 min

Last lesson the player glided perfectly through the maze. But there's still something missing — something every game in the world has but yours doesn't.

when flag clicked
set [move-speed v] to (3)
go to x: (-200) y: (-150)
forever
  set [last-good-x v] to (x position)
  set [last-good-y v] to (y position)
  if <key [right arrow v] pressed?> then
    change x by (move-speed)
  end
  if <touching color [#000000] ?> then
    set x to (last-good-x)
    set y to (last-good-y)
  end
end
        

Predict: a friend opens your maze and plays for 30 seconds. What's their first question?

Predict: if you just dropped a green goal square at the end of the maze, what's the shortest script you could add to detect "the player reached it"?

New Concept — the goal, the broadcast, the stop 15 min

A win condition has three parts. We'll build each one as its own block, then snap them together.

Part 1 — the goal pixel

On the Backdrop, pick the rectangle tool, choose a colour the maze doesn't already use (bright green #00ff00 is the standard "this is the goal" colour in retro games), and paint a small square somewhere reachable inside the maze.

Critical: when you go to write the touching-colour check, click the colour swatch in the block and use the eyedropper to sample the green directly off the Stage. Don't try to type the hex by hand. If your green is #00ff00 but the block holds #00fe00, the check never fires.

Part 2 — the detection

Inside the player's forever loop, add one more if-then:

if <touching color [#00ff00] ?> then
  broadcast (win v)
end
        

Part 3 — the reaction

Add a new sprite-wide hat on the Stage (or any sprite, but the Stage is the natural home for backdrop switches):

when I receive (win v)
switch backdrop to [You Win v]
stop [all v]
        

Why a broadcast instead of putting switch backdrop directly in the player's if-then? Because more than one sprite needs to react to the win — the music sprite stops, the enemy sprites freeze, the backdrop changes. A broadcast is a radio call: any sprite that's listening reacts. It scales as your game grows.

Multi-stage wins with lists

"Walk to the green square" is the simplest win. A more interesting game asks: collect three keys, then reach the goal. Use a list to track progress.

Make a list called keys-found. On the player, add one if-then per key colour:

forever
  if <touching color [#ffff00] ?> then
    add [yellow] to [keys-found v]
    broadcast (yellow-collected v)
  end
  if <touching color [#ff00ff] ?> then
    add [pink] to [keys-found v]
    broadcast (pink-collected v)
  end
  if <touching color [#00ff00] ?> then
    if <(length of [keys-found v]) = (3)> then
      broadcast (win v)
    end
  end
end
        

Each key sprite hides itself when its broadcast fires (when I receive [yellow-collected v] → hide) — that way the player can't re-touch a collected key and add "yellow" to the list twice.

Worked Example — the green-square finish 12 min

Open the L03-34 glider project. We'll add the simplest possible win — reach the green square, see "You Win", game over — in eight steps.

Step 1 — Paint the goal

Click the backdrop in the sprite panel. Pick the rectangle tool. Set fill to bright green (#00ff00). Paint a square about 30×30 in the upper-right of the maze, somewhere reachable but not too easy.

Step 2 — Make the "You Win" backdrop

Backdrops tab → choose a new backdrop (or paint a fresh one). Add a big "You Win!" text in the centre, maybe with some confetti emojis you draw. Rename it to You Win (lowercase "you win" works too — just match the case in the block dropdown).

Step 3 — Open the player sprite

Click the player sprite. Find the big forever loop from L03-34. We'll add to it.

Step 4 — Add the goal-detection if-then

Inside the forever, after the wall-bump rollback, drop one more if <> then. Diamond gets touching color [#00ff00] ? — use the eyedropper on your green goal square.

Step 5 — Broadcast "win"

Inside the new if-then: broadcast (win v). Click the dropdown → New message → name it win.

Step 6 — Switch to the Stage

Click the Stage in the sprite panel. New script.

Step 7 — Receive the broadcast

From Events: when I receive (win v). From Looks: switch backdrop to [You Win v].

Step 8 — Stop everything

From Control: stop [all v]. Snap it under the switch-backdrop. Done.

Click the flag. Drive the player to the green square. The backdrop should flip and the player should freeze mid-stride.

The full assembled stacks

when flag clicked
go to x: (-200) y: (-150)
forever
  set [last-good-x v] to (x position)
  set [last-good-y v] to (y position)
  if <key [right arrow v] pressed?> then
    change x by (move-speed)
  end
  if <key [up arrow v] pressed?> then
    change y by (move-speed)
  end
  if <touching color [#000000] ?> then
    set x to (last-good-x)
    set y to (last-good-y)
  end
  if <touching color [#00ff00] ?> then
    broadcast (win v)
  end
end
        

when I receive (win v)
switch backdrop to [You Win v]
stop [all v]
        

What you just built: a real game. A start state, a player, a goal, a victory. From here, everything else (lives, score, multiple levels) is decoration. The skeleton is complete.

Try It Yourself — three goal drills 15 min

when I receive (win v)
play sound [Win v] until done
switch backdrop to [You Win v]
stop [all v]
          

when flag clicked
set [time-taken v] to (0)
forever
  wait (1) seconds
  change [time-taken v] by (1)
end
          

when flag clicked
delete all of [keys-found v]
forever
  if <touching color [#ffff00] ?> then
    if <not <[keys-found v] contains [yellow] ?>> then
      add [yellow] to [keys-found v]
      broadcast (got-yellow v)
    end
  end
  if <touching color [#00ff00] ?> then
    if <(length of [keys-found v]) = (3)> then
      broadcast (win v)
    end
  end
end
          

Mini-Challenge — the flickering finish 5 min

"Aaron's flashing You-Win"

Aaron built the basic green-square finish. It almost works — but when the player touches the goal, the "You Win" backdrop flashes on and off rapidly, the player keeps moving, and the cat ends up halfway off the screen. He shows you this:

when flag clicked
forever
  if <touching color [#00ff00] ?> then
    broadcast (win v)
  end
end
        

when I receive (win v)
switch backdrop to [You Win v]
        

The win broadcast fires every frame the player is touching green — that's many times a second. What's missing, and how do you fix the flicker?

when I receive (win v)
switch backdrop to [You Win v]
stop [all v]
          

Recap 3 min

You turned a maze into a game by adding a goal, a broadcast, and a stop. The player detects the cheese pixel with the same touching color pattern used for walls, then fires a broadcast that the Stage (and any other sprite) listens for. The Stage switches to a "You Win" backdrop and calls stop [all v] to freeze every script in the project. The maze finally has a finish line.

Win condition

The rule that decides "the player has won". Always a boolean — touching a colour, list reaching a length, score above a number, etc.

Broadcast / receive

Scratch's message system. One sprite shouts; every sprite that's listening reacts. The cleanest way to fan one event out to many sprites.

stop [all v]

The Control block that halts every script in the project. Essential for any game with a definite end — without it, the win event fires forever and the game keeps running underneath.

Multi-stage win

A win condition that needs several smaller goals first. Implemented with a list or counter that the final check inspects before broadcasting "win".

Goal pixel

A specific colour painted on the backdrop (or a sprite) that the player must touch. Always sample with the eyedropper to guarantee an exact match.

Homework 2 min

The Three-Key Quest. Extend your maze into a real mini-game.

1. Open HW-L3-34-Glider.sb3. Save it as HW-L3-35-Quest.sb3.
2. Paint a small green square in the hardest-to-reach corner of the maze as the final goal.
3. Create three key sprites (paint a small yellow key, pink key, cyan key) and drop each one somewhere in the maze.
4. Create a list keys-found. Show it on the Stage so the player can see their progress.
5. Player script: each coloured key adds to the list and broadcasts a "got-X" message. The green-goal check only broadcasts "win" if the list length is 3.
6. Key scripts: each key hides on its matching broadcast.
7. Stage: at when ⚑ clicked, delete all of [keys-found v] and switch to the maze backdrop. On when I receive (win v), switch to "You Win" and stop [all v].

Bring back next class:

• The .sb3 file.
• One sentence answering: "What happens if you forget the delete all of [keys-found v] on flag-click? Try it."
• One sentence answering: "Why does the win logic live on the player and the backdrop-switch live on the Stage?"

Heads up for next class: SCR-L03-36 adds enemies — patrol sprites that walk the maze using the same wall-detection pattern, and a lives system so the player can die (and respawn) instead of just winning.