Learning Goals 3 min
By the end of this lesson you will be able to:
- Find the switch backdrop to [backdrop1 v] block in the Looks category.
- Open its dropdown and pick a named backdrop.
- Build a 3-block script that flips the Stage to the Beach the moment you click the cat.
Warm-Up 7 min
Last lesson you added a kampung day backdrop and a kampung night backdrop. Today, a single block flips the Stage between them — no mouse needed.
Quick-fire puzzle
Mei Ling has two backdrops: backdrop1 (white) and Forest. She built this script. What does the Stage look like after one flag click?
when flag clicked
switch backdrop to [Forest v]
Reveal the answer
The Stage switches from white to the Forest backdrop instantly. Click the flag again — the Stage is already Forest, so nothing visible changes. The block runs every time, but the picture is already correct.
New Concept — the switch backdrop block 15 min
Last lesson you switched backdrops with the mouse — clicking each one in the Backdrops list. That works for setup, but not for a story. In a story, you want the Stage to change on its own at the right moment. That's what the switch backdrop block is for.
The new block
| Block | Category | What it does |
|---|---|---|
| switch backdrop to [backdrop1 v] | Looks | Changes the Stage to the named backdrop. The dropdown lists every backdrop in your project. |
The dropdown
The little v at the end of the block's white box is a dropdown arrow. Click it and you'll see one entry for every backdrop you have. If you have backdrop1, Forest, and Beach Malibu, the menu shows all three. Pick one — that's the backdrop the block will switch to.
| Dropdown item | Effect |
|---|---|
| any backdrop name | Switches the Stage to that exact backdrop. |
next backdrop | Moves to the next backdrop in the list (we use this in SCR-L01-32). |
previous backdrop | Moves to the one before. Less common. |
random backdrop | Picks one at random each time the block runs. |
Sprite scripts can change the Stage
Here is the surprise: this block is in Looks, and it works inside a sprite's script as well as in the Stage's own scripts. The cat can change the Stage's backdrop. Just like a stagehand pulling a curtain.
Why it matters
Storytellers move sets between scenes; game makers swap levels; quiz designers show a new question screen. All of those are scene changes, and the switch backdrop block is the cleanest way to do them in Scratch.
Worked Example — click the cat, go to the beach 15 min
Open Scratch. Make sure your project has the two kampung backdrops from last lesson: Kampung Day (bright sky, green field) and Kampung Night (dark sky, moon). If they are missing, add them from the library using the lesson 30 method.
Step 1 — Select the cat
In the Sprite list (bottom-right), click the cat. Click the Code tab in the middle column. Your old scripts may still be there — leave them for now.
Step 2 — Drag the events hat
Open the yellow Events category. Drag when this sprite clicked into an empty spot in the Script Area. (You met this hat in SCR-L01-17.)
Step 3 — Drag the switch backdrop block
Open the purple Looks category. Scroll down until you find switch backdrop to [backdrop1 v]. Drag it under your hat. They snap together.
Step 4 — Open the dropdown
Click the small white box on the block. A menu appears, showing every backdrop in your project: backdrop1, Beach Malibu, next backdrop, previous backdrop, random backdrop. Click Beach Malibu.
Step 5 — Add a say block (so the cat says hi)
Still in Looks, drag say [Hello!] for (2) seconds under the switch block. Change Hello! to Malam dah tiba! ("Night has come!" in Malay).
Step 6 — Test
Make sure the Stage starts on Kampung Day. Then click the cat on the Stage. Three things happen, in order:
- The Stage flips to
Kampung Night— instant. - A speech bubble appears: "Malam dah tiba!"
- After 2 seconds the bubble disappears.
What changed: compared to last lesson, the cat now controls the Stage. The script changed the scene — no mouse, no human. That's the difference between editor-time setup and run-time behaviour.
The full assembled stack (your reference)
when this sprite clicked
switch backdrop to [Kampung Night v]
say [Malam dah tiba!] for (2) seconds
Try It Yourself — three small builds 12 min
Goal: Add a third backdrop (e.g. Forest) and a second script. When you press the space key, the Stage should switch to Forest.
when [space v] key pressed
switch backdrop to [Forest v]
Think: You now have two scripts on the cat. Clicking the cat sends you to the Beach; pressing space sends you to the Forest. Different events, same Stage.
Goal: Reset the scene on green flag. Add a third script so the Stage always starts on backdrop1 (white) whenever you click the flag.
when flag clicked
switch backdrop to [backdrop1 v]
say [Where shall we go?] for (2) seconds
Think: Resetting at flag click is a great habit — it stops the project starting on a random scene from last run.
Goal: Use the random backdrop option. Add a fourth backdrop or two so there are at least four. Build this script — every key press shuffles the Stage.
when [r v] key pressed
switch backdrop to [random backdrop v]
Think: The dropdown's random backdrop picks a new one each time. Press R many times — the Stage keeps surprising you.
Mini-Challenge — three scenes, three triggers 5 min
"Tour guide cat"
Set up a project with three backdrops: a starting screen, a forest, and a beach. The cat must be able to lead the audience to each scene with a different event.
It works if:
- Green flag clicked → Stage shows the starting scene (e.g.
backdrop1) and the cat says "Where to?". - Press F → Stage switches to
Forest. - Press B → Stage switches to
Beach Malibu. - You only used today's switch backdrop block plus events and Looks blocks from earlier lessons.
Reveal one valid solution
Three scripts on the cat, three different hat blocks, three different backdrops in each switch backdrop dropdown.
when flag clicked
switch backdrop to [backdrop1 v]
say [Where to?] for (2) seconds
when [f v] key pressed
switch backdrop to [Forest v]
when [b v] key pressed
switch backdrop to [Beach Malibu v]
Three scripts, three triggers. Each one is short — that's the Scratch style. Many small scripts beat one big tangled one.
Recap 2 min
Today you met the switch backdrop to [backdrop1 v] block — Scratch's way of changing the Stage from inside a script. The dropdown lists every backdrop in your project plus three special options: next, previous, random. Sprite scripts can flip the Stage, which means the cat can lead the audience between scenes.
- switch backdrop (block)
- A Looks block that changes the Stage to the chosen backdrop. The dropdown lists every backdrop in your project.
- Dropdown
- The small triangle next to a block input that opens a menu of named choices.
- Scene change
- When the Stage swaps backdrops mid-project — a key move for stories and games.
Homework 1 min
The two-room cat. Build a project where the cat changes the Stage to one of two scenes, depending on which key you press.
- Add two backdrops besides
backdrop1— e.g.Bedroom 1andCastle 2(both in the library). - Set the project to start on
backdrop1via a green-flag script. - Add a "press 1 → switch to Bedroom 1" script.
- Add a "press 2 → switch to Castle 2" script.
- Make the cat say a one-word reaction in each scene ("Sleepy!", "Wow!").
Bring back next class:
- A screenshot of your Script Area showing all three scripts.
- Your written answer: "What is the difference between clicking a backdrop in the Backdrops list, and using the switch backdrop block?"
Heads up for next class: SCR-L01-32 builds a two-scene story with the next backdrop option and a story script — kitchen to playground, in one click.