:root {
        --bg: #f0f2f5;
        --card: #ffffff;
        --primary: #4CAF50;
        --primary-dark: #3e9c43;
        --primary-active: #144917;
        --border: #ddd;
    }
    body {
        font-family: "Segoe UI", Roboto, sans-serif;
        background: var(--bg);
        margin: 0;
        padding: 30px;
    }
    .container {
        max-width: 950px;
        margin: auto;
        background: var(--card);
        padding: 25px 30px;
        border-radius: 12px;
        box-shadow: 0 8px 18px rgba(0,0,0,0.08);
    }
    h1 {
        text-align: center;
        margin-bottom: 25px;
        font-weight: 600;
        color: #333;
    }
    section {
        margin-bottom: 35px;
    }
    h2 {
        border-bottom: 2px solid var(--border);
        padding-bottom: 6px;
        margin-bottom: 18px;
        color: #444;
    }
    label {
        display: block;
        margin-bottom: 8px;
        font-weight: 600;
    }
    input[type="text"], input[type="color"], input[type="range"] {
        width: 100%;
        padding: 10px 12px;
        margin-bottom: 15px;
        border: 1px solid var(--border);
        border-radius: 6px;
        box-sizing: border-box;
        font-size: 15px;
    }
    button {
        background: var(--primary);
        color: #fff;
        border: none;
        border-radius: 6px;
        padding: 12px 20px;
        font-size: 16px;
        cursor: pointer;
        transition: background 0.2s ease;
        margin-right: 10px;
    }
    button:hover {
        background: var(--primary-dark);
    }
    .preview {
        text-align: center;
        background: var(--card);
        padding: 20px;
        border: 1px solid var(--border);
        border-radius: 12px;
    }
    .qr-wrap {
        display: inline-block;
        background: #fff;
        padding: 12px;
        border-radius: 8px;
        margin-top: 10px;
    }