Catch the Kuih — the full build & ship

Learning Goals 3 min

By the end of this lesson you will have:

1. Built a complete, playable Catch the Kuih game from a blank project — a basket that follows your control, kuih clones falling from the top, a Score that climbs, Lives that shrink, a speed-up, and a game-over screen.
2. Wired together every arc-G block — create clone of [myself v], when I start as a clone, change [score v] by (1), broadcast (game over v) — into one project with no orphan scripts.
3. Shipped it — saved L02-41-Catch-the-Kuih.sb3 and shared it (with a grown-up's help for under-13s).

Warm-Up — what we're building 5 min

This is the lesson where every piece of arc G clicks together. You've spent four lessons learning the parts:

• L02-37 — clones (spawning falling kuih).
• L02-38 — catch & reset (the basket scores and snaps the kuih back).
• L02-39 — score & game over (lives + the broadcast).
• L02-40 — levelling up speed (difficulty scaling with mod).

Today, no new blocks. Just assembly. By the end of the hour your game will look like the preview above.

Keep your L02-40 project open in another tab in case you need to peek. But build today's game from a fresh project — assembling from memory is the best test that the arc has stuck.

The Game Plan 5 min

Before we type a block, here's the whole game on a napkin. Three sprites and the Stage:

• Basket (the catcher) — follows the mouse along the bottom.
• Kuih (the falling food) — hidden original. Spawns clones every ~1 second. Clones fall, get caught, or hit the ground.
• Stage — owns the variables (score, lives, fall-speed), the two backdrops (Play and Game Over), and the flag-click setup.

The arc-G blocks we lean on, in order of first use:

when flag clicked
set [score v] to (0)
set [lives v] to (3)
set [fall-speed v] to (5)
        

The Build — ten steps from blank project to playable game 28 min

Open Scratch. Start a brand-new project. Delete the cat (right-click → delete). Now we build.

Step 1 — Backdrops

Click the Stage in the bottom-right. Open the Backdrops tab. Add two: a city/KL-skyline one and a plain one to repurpose. Rename them Play and Game Over. Open the paint editor for Game Over, use the text tool, type GAME OVER big in the centre. Save.

Step 2 — Make the three variables

Variables palette → Make a Variable. Create three, all For all sprites: score, lives, fall-speed. Tick all three checkboxes. Drag the watchers — score top-left, lives top-right, fall-speed under score (small).

Step 3 — Stage setup script

On the Stage:

when flag clicked
switch backdrop to [Play v]
set [score v] to (0)
set [lives v] to (3)
set [fall-speed v] to (5)
        

Step 4 — The basket sprite

Sprite picker → paint a tray/basket (a flat rectangle with two little handles), or use the built-in Bowl. Name it Basket. Add the mouse-follower:

when flag clicked
go to x: (0) y: (-150)
forever
  set x to (mouse x)
end
        

Step 5 — The kuih sprite

Sprite picker → paint or upload a kuih. Simplest: a small coloured ball in a kuih colour (kuih lapis = pink-and-green, ondeh-ondeh = green, bahulu = golden). Name it Kuih. Hide the original at the start:

when flag clicked
hide
        

Step 6 — The spawner

Still on the Kuih, add a second script that fires clones from the top every second:

when flag clicked
forever
  create clone of [myself v]
  wait (1) seconds
end
        

Step 7 — The clone's fall + catch detection

Still on the Kuih, add the when I start as a clone hat. Each clone places itself at a random x along the top, then falls until caught or missed:

when I start as a clone
show
go to x: (pick random (-220) to (220)) y: (170)
forever
  change y by ((0) - (fall-speed))
  if <touching [Basket v] ?> then
    change [score v] by (1)
    if <((score) mod (5)) = (0)> then
      change [fall-speed v] by (1)
    end
    delete this clone
  end
  if <(y position) < (-160)> then
    change [lives v] by (-1)
    delete this clone
  end
end
        

Step 8 — Game-over detection on the Stage

Back to the Stage. Add a watcher that ends the game when lives hits zero:

when flag clicked
forever
  if <(lives) < (1)> then
    broadcast (game over v)
    switch backdrop to [Game Over v]
    stop [this script v]
  end
end
        

Step 9 — Stop the kuih on game-over

Back to the Kuih sprite. Add the receiver that stops the rain:

when I receive (game over v)
stop [other scripts in sprite v]
hide
        

For a tighter finish, add this on the clone path too:

when I receive (game over v)
delete this clone
        

Step 10 — Playtest and save

Click the flag. The KL backdrop shows. The basket pins to your mouse. Every second a kuih drops from a random x. Catch one — score 1. Catch five — fall-speed jumps to 6 and the next kuih is faster. Miss three — lives hits 0, the backdrop flips to GAME OVER, and the sky stops raining kuih.

Save the project. File → Save to your computer → L02-41-Catch-the-Kuih.sb3.

What you just built: a complete arcade game. Three sprites, several scripts, three variables, two backdrops, one broadcast. Every block was something you met in arc G. The arc is now finished.

Three Extensions — pick at least one 10 min

when I start as a clone
switch costume to (pick random (1) to (3))
show
go to x: (pick random (-220) to (220)) y: (170)
          

when flag clicked
switch backdrop to [Start v]
set [score v] to (0)
set [lives v] to (3)
set [fall-speed v] to (5)
        

when stage clicked
switch backdrop to [Play v]
broadcast (start game v)
          

when I receive (game over v)
if <(score) > (high-score)> then
  set [high-score v] to (score)
end
          

Ship It — save, share, show the world 3 min

Polish first (5 minutes, in order)

1. Sound on catch. Add start sound [Pop v] inside the catch if-then. A tiny reward per catch.
2. Sound on miss. Add start sound [Boing v] inside the miss if-then. The player learns the two sounds fast.
3. A title. On the Play backdrop, paint "🍡 Catch the Kuih" across the top so the game has a name.
4. Final score on Game Over. On the Stage's game-over handler, add say (join [Final score: ] (score)) for (5) seconds.

Don't over-polish before a friend has played v1. Perfectionism kills more games than bugs do.

Save it

File → Save to your computer → L02-41-Catch-the-Kuih.sb3. Keep this file safe — it is the whole game in one piece, openable on any Scratch.

Share it

If you have a scratch.mit.edu account: open the project online, click Share, then fill the Instructions ("Move the basket with your mouse. Catch the kuih, don't miss!") and Notes & Credits. Copy the project URL to show your class.

Recap — arc G done 3 min

You built a complete arcade game from scratch in 60 minutes, using only blocks you'd already met. The basket follows the mouse. The kuih original is a clone factory. Each clone falls, catches, or misses, mutating two shared variables along the way. The Stage watches one variable for the game-over condition and fires a broadcast every kuih hears. The full game is three sprites, fewer than 30 blocks, and feels like many published Scratch games. That's the whole point of arcs — small pieces, big result — and you shipped it.

Capstone

A Build lesson at the end of an arc where every block is assembled into one complete, shippable project. Today was arc G's capstone.

Singleton sprite

A sprite that exists exactly once — the Basket, the Stage. Their forever loops run once. Contrast cloned sprites, where the loop runs once per clone.

Shared variable

A variable made For all sprites. Any sprite or clone can read or write it. score, lives, fall-speed are all shared.

Ship

To save a finished project and share it — as an .sb3 file or a scratch.mit.edu link. A game isn't done until someone else can play it.

Game loop

The repeated cycle of "do something, check something, react". Each clone's loop is one; the Stage's lives-watcher is another. A game is many running in parallel.

Homework — extend with bad kuih 2 min

The Burnt-Kuih Hazard. Add a second falling sprite — a burnt kuih (or a fly, or a chilli) the player shouldn't catch. Catching one costs a life. Missing it is fine.

1. Open today's L02-41-Catch-the-Kuih.sb3. Save as HW-L2-41-Bad-Kuih.sb3.
2. Paint a new sprite Bad Kuih — same shape but blackened, or a fly, whatever signals "don't catch me".
3. Give it the same hide-on-flag + spawner pattern, but a longer wait (maybe 3 seconds — bad kuih should be rarer).
4. Its clone-fall is almost identical, but the catch is the opposite: catching it does change [lives v] by (-1) instead of scoring. Missing it does nothing — just delete.
5. Give it a different sound on catch (low buzz, not pop) so the player learns the cue.

Playtest at least five rounds. The game should now reward aim — sliding under good kuih, away from bad kuih.

Bring back next class:

• The .sb3 (or your shared project link).
• A screenshot of your best score.
• Your answer to: "Arc G is now done. Which lesson from L02-37..41 was the hardest, and why?"

Heads up for next class: SCR-L02-42 · Simple Pong kicks off the next cluster. We leave catching games behind for a one-paddle Pong with a bouncing ball — your first taste of velocity: a sprite has both a position and a speed, and the speed is a variable too.