CSS :root Pseudo Class - Playground Example

<!DOCTYPE html><html><head><style type="text/css">/* 1. Define global variables here */
:root {
    --primary-color: #3498db;
    --secondary-color: #2ecc71;
    --text-color: #2c3e50;
    --bg-color: #f4f4f4;
    --padding-standard: 20px;
    --border-radius: 8px;
}

/* 2. Use variables throughout the stylesheet */
body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
}

.container {
    background: white;
    padding: var(--padding-standard);
    border-radius: var(--border-radius);
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    text-align: center;
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: background 0.3s ease;
}

.btn-primary:hover {
    background-color: var(--secondary-color);
}</style></head><body><div class="container">
        <h1>Welcome to My Site</h1>
        <p>This page uses CSS variables defined in the :root selector.</p>
        <button class="btn-primary">Click Me</button>
    </div></body></html>