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Introduction to Sequencing, Loops, and Simple Animation in Scratch

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Week 8 – Sequencing, Loops, and Simple Animation in Scratch

📅 Week 8

Sequencing, Loops & Simple Animation in Scratch

Building foundational programming logic through ordered instructions and repetition

🎯 Period 1 Objective

Scratch Basics – Sequences & Loops

Students will learn to recognise and apply two core programming concepts—sequences (the ordered flow of instructions) and loops (repeating blocks of code)—using Scratch.

📝 Detailed Notes

Core Concepts

🔹 Sequence

A sequence refers to the precise order in which instructions are carried out. In Scratch, blocks run from top to bottom inside a script. Changing the order changes the outcome—just like following steps in a recipe.

🔹 Loop (Repetition)

A loop allows a set of blocks to repeat automatically, saving time and making code more efficient. Two main types are introduced:

forever Forever block: Repeats everything inside it continuously until the program is stopped. Ideal for actions that should keep happening (e.g., movement, background music, animation cycles).

repeat [10] Repeat block: Repeats the enclosed blocks a specific number of times. Useful for finite tasks, such as drawing a shape or moving a set number of steps.

💻 Example Script – "Square Dance"

Putting It Together

This script makes the sprite trace a square path repeatedly. Each side consists of moving 100 steps and turning 90 degrees. The wait block adds a short pause between movements, making the motion easy to follow. Because the forever loop is used, the sprite dances around the square indefinitely.

when 🟢 green flag clicked
forever
    move 100 steps
    turn right 90 degrees
    wait 1 seconds
end
            

Explanation: The forever loop ensures the pattern repeats endlessly. Each iteration draws one side of the square (move forward, then rotate 90°). After four iterations, the sprite returns to its starting position and continues looping.

🎯 Period 2 Objective

Practical Application – Create a Simple Animation

Students will put sequences and loops into practice by building a continuous, interactive animation—a bouncing ball that reacts to the stage edges.

🧪 Practical Task – "Bouncing Ball"

Goal

Program a ball to move around the stage and bounce off the edges, creating a lively screen-saver-style animation that runs continuously.

📋 Step-by-Step Instructions

Set up the project: Choose a ball sprite (e.g., "Beachball" or "Tennis Ball") and select a simple backdrop, such as a solid colour or a court/field.
Start the script: Drag a when green flag clicked block into the scripting area to trigger the program when the flag is pressed.
Add continuous motion: Attach a forever block directly beneath the event block to create an infinite loop.
Define movement: Inside the forever loop, insert move 10 steps. This controls the ball's speed (increase the number to make it faster).
Enable edge detection: Directly below the move block, add the if on edge, bounce block (found in the Motion category). This detects when the sprite touches any edge of the stage and reverses its direction automatically.
Run and observe: Click the green flag and watch the ball travel in straight lines, bouncing off all four walls of the stage.

🚀 Suggested Enhancements

Differentiation & Extension Ideas

🔊 Add sound feedback: Place the play sound [pop] block inside the forever loop. Each time the sprite touches an edge, a popping sound will play—giving audio confirmation of the bounce.

🌀 Create a spinning effect: If the chosen ball sprite has multiple costumes (e.g., slightly rotated versions), insert the next costume block inside the loop. This flips through costumes, making the ball appear to spin as it moves.

⚡ Change speed on click: Experiment with changing the value inside move [10] steps to 15 or 20 to see how speed affects the animation's feel.

🎨 Trail effect: Use the stamp block (from the Pen extension) inside the loop to leave a visual trail behind the ball as it bounces around the stage.

💡 Key Takeaways for Students

What We Learned Today

A sequence is the ordered flow of instructions—code runs from top to bottom.
A forever loop keeps an action going endlessly—ideal for continuous animation.
The repeat [ ] loop runs a block a specific number of times—great for finite tasks.
Combining motion and sensing blocks enables sprites to react to their environment.
Adding sound and costume changes makes projects more interactive and engaging.
Small changes to values (like step count) can dramatically alter how an animation looks and feels.

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