What is a Costume in Scratch?

 In the context of Scratch and Object-Oriented Programming (OOP), Costumes represent the visual state or the "skin" of a Sprite. Here is a detailed explanation in English.

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What is a Costume?

A Costume is one of many possible appearances for a Sprite. While a Sprite is the "object" that contains the logic (scripts), the Costume determines what the user actually sees on the Stage at any given moment.

1. The Role of Costumes in OOP

In programming terms, Costumes are part of an object's Attributes or State.

• State Management: Changing a costume is essentially changing a "property" of the Sprite object. For example, a Sprite named "Character" might have a state called walking and another called jumping. Each state is represented by a different costume.

2. Key Features of Costumes

• Animation: By rapidly switching between different costumes (e.g., "costume1" and "costume2"), you create the illusion of motion, such as a character walking or a bird flapping its wings.

• Vector vs. Bitmap: Scratch allows two types of costumes:

  • Vector: Images made of mathematical paths (lines and curves). They stay sharp when resized.

  • Bitmap: Images made of pixels (like a photo). They can become "pixelated" or blurry when stretched.

• Center Point (Costume Center): Every costume has a center. When you tell a Sprite to go to x:0 y:0, Scratch aligns the costume center to that coordinate.

3. How to Control Costumes via Code

You use the Looks category blocks to manipulate costumes. Common blocks include:

• switch costume to [costume name]: Directly changes the appearance to a specific frame.

• next costume: Cycles through the list of costumes (perfect for loops).

• costume [number or name]: A reporter block that tells the script which costume is currently active.

4. Practical Example

Imagine a "Traffic Light" Sprite:

• Costume 1: Red light image.

• Costume 2: Yellow light image.

• Costume 3: Green light image.

The Object (the Traffic Light) remains the same, but its State (the color shown) changes by switching costumes based on a timer script.

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Summary Table: Costumes in Programming

Feature	Programming Concept	Why it matters
Appearance	Visual Attribute	Defines how the object is rendered on screen.
Switching Costumes	State Transition	Allows the object to react visually to logic (e.g., getting hit).
Costume Name/Number	Property / Variable	Allows the code to "check" what the object looks like before acting.

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Would you like to know how to use the "Next Costume" block inside a loop to create a smooth walking animation?