variables, also called custom properties, allow you to store reusable values in a CSS file. They act like placeholders for values (e.g., colors, fonts, sizes) that you can reference throughout your stylesheet.

Key Features:

Advantages of CSS Variables**

  1. Reusability: Define a value once and reuse it across the stylesheet.
  2. Maintainability: Update the variable to instantly reflect changes wherever it is used.
  3. Dynamic Updates: CSS variables can be manipulated via JavaScript to create dynamic themes.

Example: CSS Variables in Action

HTML File (index.html) 

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS Variables Example</title>
    <link rel="stylesheet" href="styles.css">
</head>
<body>
    <header>
        <h1>Welcome to My Website</h1>
    </header>
    <main>
        <p>This is an example of using CSS variables to style a web page.</p>
        <button>Click Me</button>
    </main>
</body>
</html>

CSS File (styles.css) 

/* Global variables defined in :root */
:root {
    --primary-color: #4CAF50;
    --secondary-color: white;
    --text-color: #333;
    --font-size: 16px;
    --button-radius: 8px;
}

/* Apply variables */
body {
    font-family: Arial, sans-serif;
    font-size: var(--font-size);
    background-color: var(--secondary-color);
    color: var(--text-color);
    margin: 0;
    padding: 0;
}

header {
    background-color: var(--primary-color);
    color: var(--secondary-color);
    text-align: center;
    padding: 1em;
}

button {
    background-color: var(--primary-color);
    color: var(--secondary-color);
    border: none;
    padding: 10px 20px;
    border-radius: var(--button-radius);
    cursor: pointer;
    font-size: var(--font-size);
}

button:hover {
    background-color: darkgreen;
}

Explanation of the Example

  1. Defining Variables:

    • Global variables like --primary-color and --font-size are defined in the :root selector, making them available throughout the stylesheet.

  2. Using Variables:

    • The var() function is used to insert variable values into CSS properties. For example: 
      color: var(--primary-color);

  3. Result:

    • The button and header share the same --primary-color, ensuring consistency. Any changes to --primary-color automatically apply to both.

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