Variables, Lists, and Data Management¶

Summary¶

Covers variables for game state, lists for collections, and variable scope concepts. This chapter covers 25 concepts from the learning graph, building on prerequisite concepts from earlier chapters.

Concepts Covered¶

This chapter covers the following 25 concepts from the learning graph:

Greater Than Operator
Equal Operator
Pick Random
Counted Repetition
Set Variable
Show Variable
Hide Variable
Variable Scope
List Creation
Block Parameters
Abstraction
Geometric Patterns
Pen Down
Pen Up
Pen Color
Pen Size
Clear Graphics
Erase All
Motion Detection
Talking Sprites
Accessibility Features
Multilingual Projects
Snap Together
Remix Exploration
Project Tags

Prerequisites¶

This chapter builds on concepts from:

Comparison Operators — Making Number Decisions!¶

Greater Than Operator (>)¶

< (10) > (5) >

True if left number is BIGGER than right number.

Example	Result
`10 > 5`	True ✅
`5 > 10`	False ❌
`10 > 10`	False ❌ (not greater, equal)

Use for: High score checks, boundary limits, "is big enough?"

Equal Operator (=)¶

< (10) = (10) >

True if both numbers are EXACTLY the same.

Example	Result
`10 = 10`	True ✅
`10 = 5`	False ❌
`0 = 0`	True ✅

Use for: Exact matches, "did we reach exactly 100?", "is timer 0?"

All Three Comparison Operators¶

Block	Symbol	True When...	Memory Trick
`< >`	<	Left SMALLER than right	"Less than" points to smaller
`< >`	>	Left BIGGER than right	"Greater than" points to bigger
`< = >`	=	Left EQUALS right	Two lines = same

Random Numbers — Pick Random!¶

Pick Random Block (Operators → Green)¶

pick random (1) to (10)

Gives a random whole number between the two numbers (including both!).

Random Number Uses¶

Code	Range	Use For
`pick random 1 to 6`	1–6	Dice roll
`pick random 1 to 100`	1–100	Percent chance (1% each)
`pick random -10 to 10`	-10 to 10	Random direction
`pick random 0 to 360`	0–360	Random angle

Random in Action¶

Random Spawn Position¶

when I start as a clone
go to x: (pick random -200 to 200) y: (pick random -150 to 150)

Random Chance (20% = 1 in 5)¶

if < (pick random 1 to 5) = 1 > then
    // 20% chance!
    broadcast [rare-item v]
end

Random Wait¶

forever
    wait (pick random 1 to 3) secs
    create clone of [myself v]
end

Counted Repetition — Exact Loops!¶

Repeat Block (Control → Orange)¶

repeat (10)
    move 10 steps
    turn 15 degrees
end

Runs exactly N times — perfect when you know how many!

Counted Repeat Examples¶

Draw a Polygon¶

repeat (5)        // Pentagon
    move 100 steps
    turn 72 degrees    // 360/5 = 72
end

Spawn Exact Number¶

repeat (10)
    create clone of [myself v]
    wait 0.5 secs
end

Countdown¶

set [countdown v] to (10)
repeat (10)
    say (countdown) for 1 secs
    change [countdown v] by (-1)
end

Variable Basics — Your Data Boxes!¶

What Is a Variable?¶

A variable is a named box that holds one value that can change.

set [score v] to (0)    // Put 0 in the "score" box
change [score v] by (10)  // Add 10 to the box

Variable Blocks (Variables → Red)¶

Block	What It Does
`set [name v] to (value)`	Put exact value in box
`change [name v] by (amount)`	Add/subtract from box
`show variable [name]`	Display on stage
`hide variable [name]`	Remove from stage
`variable` (reporter)	Get current value

Creating Variables¶

Click Variables (🔴 Red)
Click Make a Variable
Name it: score, lives, timer, level, high-score
Choose scope:
For all sprites = shared (one box for everyone)
For this sprite only = private (each sprite has own)
Click OK!

Variable Scope — Who Can See It?¶

Scope	Who Sees It	Use For
For all sprites	Everyone shares ONE box	Score, timer, high score, level
For this sprite only	Each sprite has own box	Player health, enemy speed, sprite state

Variable Examples¶

Score System¶

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

when I receive [coin-collected v]
change [score v] by (10)

Lives System¶

when green flag clicked
set [lives v] to (3)
show variable [lives v]

when I receive [player-hit v]
change [lives v] by (-1)
if < (lives) = 0 > then
    broadcast [game-over v]
end

Timer¶

when green flag clicked
set [timer v] to (0)
show variable [timer v]
forever
    wait (1) secs
    change [timer v] by (1)
end

Show/Hide Variables — Control the Display!¶

Show Variable¶

show variable [score v]

Displays the variable on the stage (top-left by default).

Hide Variable¶

hide variable [score v]

Removes from stage — but value still exists!

When to Show/Hide¶

Situation	Action
Game starts	`show variable [score]`, `show variable [lives]`
Menu screen	`hide variable [score]`, `show variable [high-score]`
Game over	`hide variable [lives]`, `show variable [final-score]`
Pause menu	`hide variable [timer]`

👁️ Show What Matters!

Only show variables the player needs to see right now. Too many = clutter!

Lists — Collections of Values!¶

What Is a List?¶

A list is like a variable, but holds MULTIPLE values in order — like a shopping list!

List: inventory
[0] "sword"
[1] "shield"
[2] "potion"
[3] "key"

Creating a List¶

Click Variables (🔴 Red)
Click Make a List
Name it: inventory, high-scores, level-codes, player-names
Choose scope: For all sprites or For this sprite only
Click OK!

List Blocks (Variables → Dark Red)¶

Block	What It Does
`add [thing v] to [list v]`	Append to end
`delete (1) of [list v]`	Remove item at position
`insert [thing v] at (1) of [list v]`	Insert at position
`replace item (1) of [list v] with [thing v]`	Change existing
`item (1) of [list v]`	Reporter: get value at position
`length of [list v]`	Reporter: how many items
`list contains [thing v]?`	Boolean: is it in list?
`show list [name]`	Display on stage
`hide list [name]`	Hide from stage
`delete all of [list v]`	Clear everything

List Examples¶

Inventory System¶

when green flag clicked
delete all of [inventory v]
add [sword] to [inventory v]
add [shield] to [inventory v]
show list [inventory v]

when I receive [found-potion v]
add [potion] to [inventory v]

High Score List¶

when green flag clicked
delete all of [high-scores v]
repeat 5
    add (0) to [high-scores v]
end

when I receive [new-score v]
if < (score) > (item (1) of [high-scores v]) > then
    insert (score) at (1) of [high-scores v]
    delete (6) of [high-scores v]  // Keep top 5
end

Block Parameters — Custom Block Inputs!¶

What Are Parameters?¶

Parameters are inputs for your custom blocks — like function arguments!

define jump (height)
change y by (height)
wait 0.2 secs
change y by (height * -1)

Use it: jump (100) → jumps high! jump (20) → small hop!

Adding Parameters¶

Make a Block in My Blocks (🩷 Pink)
Click Options (gear icon)
Click Add number input or Add string input
Name it: height, speed, name, color
Click OK — parameter appears in define hat!

Parameter Types¶

Type	Accepts	Example Use
Number input	Numbers	`jump (height)`, `move (steps)`
String input	Text	`say (message)`, `set name to (name)`
Boolean input	True/false	`if (condition) then`

Parameter Examples¶

Jump with Height¶

define jump (height)
change y by (height)
wait 0.2 secs
change y by (height * -1)

Use: jump (100) = high jump, jump (20) = small hop

Draw Polygon¶

define polygon (sides) (size)
repeat (sides)
    move (size) steps
    turn (360 / sides) degrees
end

Use: polygon (5) (100) = pentagon, polygon (8) (50) = octagon!

Glide to Position¶

define glide-to (target-x) (target-y) (seconds)
glide (seconds) secs to x: (target-x) y: (target-y)

Use: glide-to (100) (50) (2) — smooth move to (100, 50) in 2 secs!

Abstraction — Hiding Complexity!¶

What Is Abstraction?¶

Abstraction = hiding complex details behind a simple name.

Analogy: You press "Start" on a microwave. You don't need to know how magnetrons work — you just press "Start"!

In Scratch: Custom Blocks = Abstraction!¶

define draw-house (size)
repeat 4
    move (size) steps
    turn 90 degrees
end
move (size) steps
turn 30 degrees
repeat 3
    move (size) steps
    turn 120 degrees
end

User just types: draw-house (100) — doesn't need to know the math!

Why Abstraction Helps¶

Benefit	Explanation
Less repetition	Write once, use many times
Easier to read	`draw-house` vs 20 motion blocks
Easy to fix	Change once, fixes everywhere
Shareable	Backpack your blocks to other projects

Pen Extension Deep Dive — Drawing Details!¶

Pen Blocks Review (Pen → Green)¶

Block	What It Does
`pen down`	Start drawing trail
`pen up`	Stop drawing
`erase all`	Clear all pen marks
`set pen color to [color]`	Set exact color
`change pen color by (10)`	Cycle through colors
`set pen size to (5)`	Line thickness
`change pen size by (5)`	Thicker/thinner
`stamp`	Leave costume copy as drawing

Pen Down / Pen Up¶

pen down      // Start drawing
move 100 steps
pen up        // Stop drawing
move 50 steps // No trail

Only draws when pen is DOWN!

Pen Color¶

Block	What It Does
`set pen color to [color]`	Pick exact color
`change pen color by (10)`	Cycle through spectrum (0-200)

Pen Size¶

set pen size to (10)     // Thick line
change pen size by (5)   // Thicker
set pen size to (1)      // Thin line

Clear Graphics¶

Block	What It Does
`erase all`	Clear ALL pen marks
`clear graphics`	Same as erase all

Pen Examples¶

Rainbow Spiral¶

when green flag clicked
erase all
pen down
set pen size to 5
repeat 360
    move 5 steps
    turn 1 degrees
    change pen color by 1
end
pen up

Stamp Circle¶

when green flag clicked
erase all
pen up
repeat 12
    go to x: 0 y: 0
    move 100 steps
    stamp
    turn 30 degrees
end

Motion Detection — Camera Magic!¶

Video Sensing Recap (Extensions → Video Sensing)¶

Block	What It Does
`turn video [on v]`	Start/stop camera
`video [on v] on [stage v]`	Show/hide video
`video transparency (50)`	See-through amount
`video [motion v] on [this sprite v]`	Motion amount (0-100)
`when video [motion] > (50)`	Hat: triggers on motion

Motion Detection Example¶

when green flag clicked
turn video on
set video transparency to 50
forever
    if <video [motion] on [this sprite] > 30> then
        change color effect by 10
        play sound [pop v]
    end
end

Wave at camera → sprite reacts!

Talking Sprites — Text to Speech!¶

Text to Speech Recap (Extensions → Text to Speech)¶

Block	What It Does
`speak [Hello!]`	Speaks immediately
`speak [Hello!] and wait`	Speaks, waits for finish
`set voice to [alto v]`	Choose voice
`set language to [English v]`	Choose language

Voices: `alto`, `tenor`, `soprano`, `random`¶

Languages: English, Spanish, French, German, Chinese, Japanese, Korean...¶

Text to Speech Example¶

when green flag clicked
set voice to [tenor v]
set language to [English v]
speak [Welcome to my game!] and wait
speak [Use arrow keys to move.]

Accessibility Features — Making Games for Everyone!¶

Why Accessibility Matters¶

Games should be fun for everyone — including players with different abilities!

Scratch Accessibility Features¶

Feature	How It Helps
High contrast	Use bright colors on dark backgrounds
Text to Speech	Read text aloud for visually impaired
Large text	Big speech bubbles, large variable displays
Simple controls	One key per action, no complex combos
Visual cues	Flash, color change, not just sound
Adjustable speed	Variable for game speed

Accessible Design Tips¶

Tip	Example
Color + Shape	Red X (color) + X mark (shape) for "wrong"
Sound + Visual	Flash screen AND play sound for hit
Adjustable text	Let player choose font size
No time limits	Or make them optional
Remappable keys	Let player choose controls

Multilingual Projects — Games for the World!¶

Translate + Text to Speech = Polyglot Games!¶

when green flag clicked
set language to [Spanish v]
speak (translate [Welcome!] to [Spanish v]) and wait

Supported Languages¶

English, Spanish, French, German, Italian, Portuguese, Chinese, Japanese, Korean, Russian, Arabic, Hindi, and many more!

Multilingual Example¶

when green flag clicked
set language to [Spanish v]
speak (translate [Welcome to my game!] to [Spanish v]) and wait
wait 1 secs
set language to [French v]
speak (translate [Bienvenue dans mon jeu!] to [French v]) and wait
wait 1 secs
set language to [Japanese v]
speak (translate [ようこそ！] to [Japanese v]) and wait

Block Mechanics — Snap Together!¶

How Blocks Connect¶

Connection	How It Works
Vertical snap	Top/bottom notches click
Horizontal insert	White/hex holes accept reporters/booleans
Drag to insert	Drag between blocks — white line shows where

Snap Rules¶

Rule	Description
Hat only at top	Nothing above hat block
Cap only at bottom	Nothing below cap block
Reporters in white holes	Number/text inputs
Booleans in hex holes	True/false inputs
Stacks stack vertically	Top to bottom order

Remix Exploration — Learn from Others!¶

What Is Remixing?¶

Remixing = taking someone's project, making changes, sharing as your own!

How to Remix¶

Find a project you like
Click See Inside (view code)
Click Remix (creates your copy)
Make changes
Share — automatically credits original!

Learning from Remixes¶

What to Look For	What to Learn
How they did movement	Player controller patterns
How they did collisions	`touching color?`, `distance to`
How they managed state	Variables, lists, broadcasts
How they organized code	Custom blocks, comments, clean up

🔍 Remix = Free Tutorial!

Every remixed project is a free masterclass — see exactly how they did it!

Remix Etiquette¶

Do	Don't
Credit original (auto-added)	Claim as 100% yours
Make meaningful changes	Just change title/colors
Thank creator in notes	Claim their code as yours
Add your twist	Copy-paste without understanding

Project Tags — Help Others Find Your Game!¶

What Are Tags?¶

Tags are keywords that help people find your project in search!

Good Tags¶

Category	Example Tags
Genre	`platformer`, `rpg`, `puzzle`, `shooter`, `racing`
Style	`pixel-art`, `hand-drawn`, `3d`, `anime`, `retro`
Theme	`space`, `fantasy`, `horror`, `cute`, `educational`
Tech	`pen`, `clones`, `lists`, `video-sensing`, `microbit`
Audience	`beginner`, `kids`, `all-ages`, `challenging`

Tagging Tips¶

Tip	Why
5-10 tags max	Too many = spammy
Be specific	`platformer` better than `game`
Use popular tags	Check what similar projects use
Update tags	Add new tags when you add features

Summary¶

In this chapter, you learned:

✅ Comparison operators — >, <, = for smart decisions
✅ Random numbers — pick random for dice, spawns, chance
✅ Counted repetition — repeat (N) for exact loops
✅ Variables — Create, set, change, show/hide, scope
✅ Lists — Create, add, delete, insert, length, contains
✅ Block parameters — Custom blocks with inputs
✅ Abstraction — Hide complexity in custom blocks
✅ Pen details — Down/up, color, size, clear, stamp
✅ Motion detection — Camera-based games
✅ Text to Speech — Talking sprites
✅ Accessibility — Games for everyone
✅ Multilingual — Translate + Speech = world-ready
✅ Block snapping — How connections work
✅ Remixing — Learn by modifying others' work
✅ Project tags — Help players find your game

Key Terms to Remember¶

Term	Definition
Greater Than (>)	Left bigger than right
Equal (=)	Left exactly equals right
Pick Random	Random integer in range
Counted Repetition	`repeat (N)` exact loop
Set Variable	Put exact value in box
Show/Hide Variable	Display or hide on stage
Variable Scope	For all sprites vs this sprite only
List Creation	`make a list` for collections
Block Parameters	Inputs for custom blocks
Abstraction	Hide complexity behind simple name
Pen Down/Up	Start/stop drawing trail
Pen Color/Size	Drawing appearance
Erase All/Clear	Remove pen marks
Motion Detection	Camera-based movement sensing
Text to Speech	Synthetic voice from text
Accessibility	Design for all abilities
Multilingual	Multiple languages in one project
Snap Together	How blocks connect
Remix	Modify and share someone's project
Project Tags	Keywords for discoverability

Try It Yourself! 🎯¶

Challenge 1: Create a high score list (list) that saves top 5 scores

Challenge 2: Make a custom block draw-star (size) (points) using Pen

Challenge 3: Build a shop system — list inventory, variable coins, buy/sell items

Challenge 4: Add Text to Speech to make your game accessible (reads instructions)

Challenge 5: Remix a project from the Scratch community — add your own feature

Challenge 6: Add tags to your best project and share it

Challenge 6: Make your game multilingual — at least 3 languages

What's Next?¶

In Chapter 8, you'll explore Animation, Parallelism, and Debugging — bringing your games to life with smooth animations, multiple things happening at once, and fixing bugs like a pro!

→ Next Chapter: Animation, Parallelism, and Debugging

Variables, Lists, and Data Management¶

Summary¶

Concepts Covered¶

Prerequisites¶

Comparison Operators — Making Number Decisions!¶

Greater Than Operator (>)¶

Equal Operator (=)¶

All Three Comparison Operators¶

Random Numbers — Pick Random!¶

Pick Random Block (Operators → Green)¶

Random Number Uses¶

Random in Action¶

Random Spawn Position¶

Random Chance (20% = 1 in 5)¶

Random Wait¶

Counted Repetition — Exact Loops!¶

Repeat Block (Control → Orange)¶

Counted Repeat Examples¶

Draw a Polygon¶

Spawn Exact Number¶

Countdown¶

Variable Basics — Your Data Boxes!¶

What Is a Variable?¶

Variable Blocks (Variables → Red)¶

Creating Variables¶

Variable Scope — Who Can See It?¶

Variable Examples¶

Score System¶

Lives System¶

Timer¶

Show/Hide Variables — Control the Display!¶

Show Variable¶

Hide Variable¶

When to Show/Hide¶

Lists — Collections of Values!¶

What Is a List?¶

Creating a List¶

List Blocks (Variables → Dark Red)¶

List Examples¶

Inventory System¶

High Score List¶

Block Parameters — Custom Block Inputs!¶

What Are Parameters?¶

Adding Parameters¶

Parameter Types¶

Parameter Examples¶

Jump with Height¶

Draw Polygon¶

Glide to Position¶

Abstraction — Hiding Complexity!¶

What Is Abstraction?¶

In Scratch: Custom Blocks = Abstraction!¶

Why Abstraction Helps¶

Pen Extension Deep Dive — Drawing Details!¶

Pen Blocks Review (Pen → Green)¶

Pen Down / Pen Up¶

Pen Color¶

Pen Size¶

Clear Graphics¶

Pen Examples¶

Rainbow Spiral¶

Stamp Circle¶

Motion Detection — Camera Magic!¶

Video Sensing Recap (Extensions → Video Sensing)¶

Motion Detection Example¶

Talking Sprites — Text to Speech!¶

Text to Speech Recap (Extensions → Text to Speech)¶

Voices: alto, tenor, soprano, random¶

Languages: English, Spanish, French, German, Chinese, Japanese, Korean...¶

Text to Speech Example¶

Accessibility Features — Making Games for Everyone!¶

Why Accessibility Matters¶

Scratch Accessibility Features¶

Accessible Design Tips¶

Multilingual Projects — Games for the World!¶

Translate + Text to Speech = Polyglot Games!¶

Supported Languages¶

Multilingual Example¶

Block Mechanics — Snap Together!¶

How Blocks Connect¶

Voices: `alto`, `tenor`, `soprano`, `random`¶