Your First Variable: score — Scratch L1

WHAT IT SHOULD LOOK LIKE

Where this arc is heading: by Lesson 43 you have a real game with a score that goes up when you catch something. That orange box in the corner is what today is about.

at the start

step 1 of 2

the sprites move as they would on the real Stage

Learning Goals 3 min

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

Make a variable and explain what one actually is.
Show and hide a variable’s readout on the Stage.
Say why a loop cannot count without one.

Warm-Up 7 min

New arc, new project — and the last one of Level 1. Start fresh with a Blue Sky backdrop, a cat at the bottom and a piece of bread up above. Everything you have built so far has had one thing in common: the moment it finishes, it forgets everything.

WHAT IT SHOULD LOOK LIKE

Where this arc begins. A catcher, something to catch, and no way whatsoever to keep score.

a catcher, and something to catch

step 1 of 2

the sprites move as they would on the real Stage

Quick-fire puzzle

Wei Jie wants the cat to count its steps out loud — 1, 2, 3 and so on. He built this and every single line said the same thing. Why?


when flag clicked
repeat (5)
  move (30) steps
  say [1] for (1) seconds
end

A loop that counts to one, five times over.

Reveal the answer

The say block contains the word “1”, and a word cannot change. Every pass through the loop says exactly what is typed in the block, because there is nothing in the project capable of holding a number that grows.

He does not need a cleverer loop. He needs somewhere to keep a count — which is what a variable is.

New Concept — a box with a name 15 min

Think of a variable as a small labelled box that your project can put a number in and take a number out of. The label never changes; the contents can change as often as you like.

What a variable actually is

Two parts, and it is worth keeping them separate in your head:

A name you choose — score, lives, speed. This is fixed once you make it.
A value the project holds — 0, then 1, then 7. This changes constantly.

When a block says score, it means “whatever number is in that box right now”. That is the whole idea, and it is the thing that separates a project that reacts from a project that remembers.

One box, one name, three different moments. Blocks always refer to the label and get whatever is currently inside.

Making one

Click the dark orange Variables dot in the Blocks Panel. Back in Lesson 3 you noticed this category was nearly empty — this is why. It fills up only once you have made something.

Click Make a Variable, type a name, and press OK. The category immediately gains a set of blocks, all referring to your new variable by name.

Names matter more than you would think

Call it score and every script you write is readable a month later. Call it a and you will have no idea what it was for. This costs nothing at the time and saves a great deal later.

The readout on the Stage

Making a variable also puts a small orange box in the top-left of the Stage showing its current value. The tick box beside the variable in the Blocks Panel turns that on and off.

For a game score you want it visible. For something the player should not see — a hidden timer, a secret count — untick it.

Why it matters

Everything that makes a project feel like a game rather than an animation needs a variable. Scores, lives, levels, timers, speed. Without one, a project can only react to what is happening right now; with one, it can remember what has happened.

Worked Example — a counter that actually counts 15 min

We solve Wei Jie’s problem from the Warm-Up, which is the clearest possible demonstration of what a variable is for.

WHAT IT SHOULD LOOK LIKE

Stage plan. The readout in the corner keeps pace with the steps. That box is the variable.

at the start

step 1 of 2

the sprite moves as it would on the real Stage

Step 1 — Look at the empty category

Click the dark orange Variables dot. Almost nothing there — just two buttons. This is the category you noticed was empty back in Lesson 3.

Step 2 — Make one

Click Make a Variable. Type score. Leave “For all sprites” selected and click OK.

Two things happen at once. The category fills with blocks that did not exist a moment ago, and an orange readout appears in the corner of the Stage showing 0.

Step 3 — Find it in the block list

At the top of the Variables category there is now a small rounded block simply labelled score. That rounded shape means it holds a value — it is not something you run, it is something you use inside other blocks.

Step 4 — Drop it into a say block

Drag a say [Hello!] for (2) seconds into the Script Area, then drag the rounded score block directly into its white oval. The oval accepts it and the block now reads “say score”.


when flag clicked
say (score) for (2) seconds

The cat now says whatever number is in the box, rather than a fixed word.

Step 5 — Prove it is reading the box

Click the flag. The cat says 0. Now click directly on the readout on the Stage — you can drag it, but you cannot type into it — so instead use the Variables category and drop in a set [score v] to (0) block with 5 in it, run that, then run the say again.

The cat now says 5. Nothing about the say block changed. It reads the box every time.

Step 6 — Solve Wei Jie’s problem

Now the loop that could not count.


when flag clicked
set [score v] to (0)
repeat (5)
  change [score v] by (1)
  move (30) steps
  say (score) for (1) seconds
end

Seven blocks. The cat now genuinely counts 1, 2, 3, 4, 5.

Step 7 — Watch the readout keep pace

Run it and watch the orange box in the corner as well as the speech bubble. They change together, because they are the same number shown two ways.

Step 8 — Try it without the reset

Delete the set [score v] to (0) and run it twice. The second run counts 6 to 10, because the box still held 5 from last time.

Variables stick between runs, exactly like position, size, visibility, backdrop and volume. This is the sixth kind of state, and the habit is the same one you have built all level.

What changed: your project can hold on to a number between one moment and the next, which is the difference between reacting and remembering.

The full assembled stack (your reference)


when flag clicked
set [score v] to (0)
repeat (5)
  change [score v] by (1)
  move (30) steps
  say (score) for (1) seconds
end

A loop that counts, which was impossible an hour ago.

Try It Yourself — three small builds 12 min

🟢 Easy

Goal: Make a variable called lives, set it to 3, and have the cat announce it.


when flag clicked
set [lives v] to (3)
say (lives) for (2) seconds

Think: two variables can exist at once, each with its own box and its own readout. Making a second one does not disturb the first.

🟡 Medium

Goal: Count key presses. Every time the space bar is pressed, the score goes up by one and the readout follows.

The readout climbs with every press. Nothing on the Stage moves at all.


when [space v] key pressed
change [score v] by (1)

when flag clicked
set [score v] to (0)

Think: two separate scripts. The flag resets; the key counts. That split is exactly how a real game handles its score.

🔴 Stretch

Mini-mission: count down instead. Build a variable that goes down — three lives that reduce by one each time a key is pressed, and a message when they run out.

The same blocks with a negative number. Counting down is counting up in reverse.

It works if: the readout starts at three, falls by one per press, and the cat says something when it reaches zero. Pressing more after that should not send it negative. Keep each stack under 8 blocks.

Think: the last criterion is the hard one. With only the blocks you have so far, how could you stop it going below zero — and what would you have to reset to try again?

Mini-Challenge — the step counter 5 min

“How far did the cat walk?”

Build a cat that keeps a running total of how far it has travelled, and announces it at the end.

WHAT IT SHOULD LOOK LIKE

A running total that grows by the same amount as the cat moves. The two numbers must agree.

at the start

step 1 of 2

the sprite moves as it would on the real Stage

It works if:

One flag click runs the whole thing.
The readout shows the total distance actually travelled, not the number of steps taken.
The cat announces the final total at the end.
Running it twice gives the same answer both times.

Reveal one valid solution (teacher)


when flag clicked
set [steps v] to (0)
repeat (4)
  move (30) steps
  change [steps v] by (30)
end
say (steps) for (2) seconds

The trap is changing the variable by 1 rather than 30 — which counts moves, not distance. Both are reasonable things to count; the criterion says which one is wanted, and pupils have to read it carefully.

🚀 Mission — Set Up the Game

WHAT IT SHOULD LOOK LIKE

The pieces of the game in place: a catcher, something to catch, and a score at zero.

a game waiting to happen

step 1 of 2

the sprites move as they would on the real Stage

Set up the project the rest of this arc will build on. There is barely any code — it is about getting the pieces right.

A catcher near the bottom of the Stage and something to catch near the top.
A variable called score, visible on the Stage.
A flag script that sets the score to zero and puts both sprites on their marks.
A key that adds one to the score, so you can prove the readout works.
Each stack stays within 8 blocks.

✅ Done when: clicking the flag always shows a score of zero, however high you drove it last time. Going further: add a second variable for lives and show both.

Teacher notes — why the reset criterion matters here

“Always shows zero” is the criterion that teaches the lesson. A score that carries over between runs is the single most common bug in every catching game pupils will ever write, and meeting it now — with two blocks and no game logic in the way — makes it obvious rather than mysterious.

Recap 2 min

A variable is a labelled box holding a number. The name is fixed; the value changes. Blocks that mention it read whatever is inside at that moment, which is what lets a loop count and a game keep score. Making one fills the Variables category and puts a readout on the Stage. And like everything else in Level 1, a variable’s value survives between runs — so a game that does not reset its score will start where the last one finished.

Variable: A named box holding a value that can change while a project runs.
Value: The number currently inside the box.
Readout: The orange display on the Stage showing a variable’s current value.
For all sprites: A variable every sprite can see and change. The right choice for a score.

Homework 1 min

Two boxes. Make two variables and prove they are completely independent of each other.

Make variables called score and lives, and show both on the Stage.
Build a key script that changes only one of them.
Press it several times and confirm the other readout does not move.
Screenshot the Stage with both readouts visible.


when flag clicked
set [score v] to (0)
set [lives v] to (3)

when [space v] key pressed
change [score v] by (1)

Two boxes, one key. Only one of them should ever move.

Bring back next class:

Your screenshot.
Your answer to: “Why did Wei Jie’s loop say ‘1’ five times, and what exactly does a variable give you that a typed number cannot?”

Heads up for next class: SCR-L01-41 covers set, change and show — the three blocks that do everything a variable needs.

WHAT IT SHOULD LOOK LIKE

Where this arc is heading: by Lesson 43 you have a real game with a score that goes up when you catch something. That orange box in the corner is what today is about.

at the start

step 1 of 2

the sprites move as they would on the real Stage

Learning Goals 3 min

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

Make a variable and explain what one actually is.
Show and hide a variable’s readout on the Stage.
Say why a loop cannot count without one.

Warm-Up 7 min

WHAT IT SHOULD LOOK LIKE

Where this arc begins. A catcher, something to catch, and no way whatsoever to keep score.

a catcher, and something to catch

step 1 of 2

the sprites move as they would on the real Stage

Quick-fire puzzle

Wei Jie wants the cat to count its steps out loud — 1, 2, 3 and so on. He built this and every single line said the same thing. Why?


when flag clicked
repeat (5)
  move (30) steps
  say [1] for (1) seconds
end

A loop that counts to one, five times over.

Reveal the answer

He does not need a cleverer loop. He needs somewhere to keep a count — which is what a variable is.

New Concept — a box with a name 15 min

Think of a variable as a small labelled box that your project can put a number in and take a number out of. The label never changes; the contents can change as often as you like.

What a variable actually is

Two parts, and it is worth keeping them separate in your head:

A name you choose — score, lives, speed. This is fixed once you make it.
A value the project holds — 0, then 1, then 7. This changes constantly.

When a block says score, it means “whatever number is in that box right now”. That is the whole idea, and it is the thing that separates a project that reacts from a project that remembers.

One box, one name, three different moments. Blocks always refer to the label and get whatever is currently inside.

Making one

Click the dark orange Variables dot in the Blocks Panel. Back in Lesson 3 you noticed this category was nearly empty — this is why. It fills up only once you have made something.

Click Make a Variable, type a name, and press OK. The category immediately gains a set of blocks, all referring to your new variable by name.

Names matter more than you would think

Call it score and every script you write is readable a month later. Call it a and you will have no idea what it was for. This costs nothing at the time and saves a great deal later.

The readout on the Stage

Making a variable also puts a small orange box in the top-left of the Stage showing its current value. The tick box beside the variable in the Blocks Panel turns that on and off.

For a game score you want it visible. For something the player should not see — a hidden timer, a secret count — untick it.

Why it matters

Worked Example — a counter that actually counts 15 min

We solve Wei Jie’s problem from the Warm-Up, which is the clearest possible demonstration of what a variable is for.

WHAT IT SHOULD LOOK LIKE

Stage plan. The readout in the corner keeps pace with the steps. That box is the variable.

at the start

step 1 of 2

the sprite moves as it would on the real Stage

Step 1 — Look at the empty category

Click the dark orange Variables dot. Almost nothing there — just two buttons. This is the category you noticed was empty back in Lesson 3.

Step 2 — Make one

Click Make a Variable. Type score. Leave “For all sprites” selected and click OK.

Two things happen at once. The category fills with blocks that did not exist a moment ago, and an orange readout appears in the corner of the Stage showing 0.

Step 3 — Find it in the block list

Step 4 — Drop it into a say block

Drag a say [Hello!] for (2) seconds into the Script Area, then drag the rounded score block directly into its white oval. The oval accepts it and the block now reads “say score”.


when flag clicked
say (score) for (2) seconds

The cat now says whatever number is in the box, rather than a fixed word.

Step 5 — Prove it is reading the box

The cat now says 5. Nothing about the say block changed. It reads the box every time.

Step 6 — Solve Wei Jie’s problem

Now the loop that could not count.


when flag clicked
set [score v] to (0)
repeat (5)
  change [score v] by (1)
  move (30) steps
  say (score) for (1) seconds
end

Seven blocks. The cat now genuinely counts 1, 2, 3, 4, 5.

Step 7 — Watch the readout keep pace

Run it and watch the orange box in the corner as well as the speech bubble. They change together, because they are the same number shown two ways.

Step 8 — Try it without the reset

Delete the set [score v] to (0) and run it twice. The second run counts 6 to 10, because the box still held 5 from last time.

Variables stick between runs, exactly like position, size, visibility, backdrop and volume. This is the sixth kind of state, and the habit is the same one you have built all level.

What changed: your project can hold on to a number between one moment and the next, which is the difference between reacting and remembering.

The full assembled stack (your reference)


when flag clicked
set [score v] to (0)
repeat (5)
  change [score v] by (1)
  move (30) steps
  say (score) for (1) seconds
end

A loop that counts, which was impossible an hour ago.

Try It Yourself — three small builds 12 min

🟢 Easy

Goal: Make a variable called lives, set it to 3, and have the cat announce it.


when flag clicked
set [lives v] to (3)
say (lives) for (2) seconds

Think: two variables can exist at once, each with its own box and its own readout. Making a second one does not disturb the first.

🟡 Medium

Goal: Count key presses. Every time the space bar is pressed, the score goes up by one and the readout follows.

The readout climbs with every press. Nothing on the Stage moves at all.


when [space v] key pressed
change [score v] by (1)

when flag clicked
set [score v] to (0)

Think: two separate scripts. The flag resets; the key counts. That split is exactly how a real game handles its score.

🔴 Stretch

Mini-mission: count down instead. Build a variable that goes down — three lives that reduce by one each time a key is pressed, and a message when they run out.

The same blocks with a negative number. Counting down is counting up in reverse.

Think: the last criterion is the hard one. With only the blocks you have so far, how could you stop it going below zero — and what would you have to reset to try again?

Mini-Challenge — the step counter 5 min

“How far did the cat walk?”

Build a cat that keeps a running total of how far it has travelled, and announces it at the end.

WHAT IT SHOULD LOOK LIKE

A running total that grows by the same amount as the cat moves. The two numbers must agree.

at the start

step 1 of 2

the sprite moves as it would on the real Stage

It works if:

One flag click runs the whole thing.
The readout shows the total distance actually travelled, not the number of steps taken.
The cat announces the final total at the end.
Running it twice gives the same answer both times.

Reveal one valid solution (teacher)


when flag clicked
set [steps v] to (0)
repeat (4)
  move (30) steps
  change [steps v] by (30)
end
say (steps) for (2) seconds

🚀 Mission — Set Up the Game

WHAT IT SHOULD LOOK LIKE

The pieces of the game in place: a catcher, something to catch, and a score at zero.

a game waiting to happen

step 1 of 2

the sprites move as they would on the real Stage

Set up the project the rest of this arc will build on. There is barely any code — it is about getting the pieces right.

A catcher near the bottom of the Stage and something to catch near the top.
A variable called score, visible on the Stage.
A flag script that sets the score to zero and puts both sprites on their marks.
A key that adds one to the score, so you can prove the readout works.
Each stack stays within 8 blocks.

✅ Done when: clicking the flag always shows a score of zero, however high you drove it last time. Going further: add a second variable for lives and show both.

Teacher notes — why the reset criterion matters here

Recap 2 min

Variable: A named box holding a value that can change while a project runs.
Value: The number currently inside the box.
Readout: The orange display on the Stage showing a variable’s current value.
For all sprites: A variable every sprite can see and change. The right choice for a score.

Homework 1 min

Two boxes. Make two variables and prove they are completely independent of each other.

Make variables called score and lives, and show both on the Stage.
Build a key script that changes only one of them.
Press it several times and confirm the other readout does not move.
Screenshot the Stage with both readouts visible.


when flag clicked
set [score v] to (0)
set [lives v] to (3)

when [space v] key pressed
change [score v] by (1)

Two boxes, one key. Only one of them should ever move.

Bring back next class:

Your screenshot.
Your answer to: “Why did Wei Jie’s loop say ‘1’ five times, and what exactly does a variable give you that a typed number cannot?”

Heads up for next class: SCR-L01-41 covers set, change and show — the three blocks that do everything a variable needs.