:root {
            --primary: #e63946; /* Vibrant red */
            --primary-dark: #d00000; /* Darker red */
            --secondary: #f48c06; /* Bright orange */
            --accent: #ffba08; /* Golden yellow */
            --bg-light: #fef6e4; /* Light cream */
            --bg-dark: #1b263b; /* Dark navy */
            --card-light: #ffffff; /* White */
            --card-dark: #2a3e5a; /* Darker navy */
            --text-light: #1b263b; /* Dark navy text */
            --text-dark: #f1f5f9; /* Light text for dark mode */
            --border-light: #e2e8f0; /* Light border */
            --border-dark: #415a77; /* Dark border */
            --shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
            --shadow-lg: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
            --transition: all 0.3s ease;
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
        }

        body {
            line-height: 1.6;
            min-height: 100vh;
            background: linear-gradient(135deg, var(--bg-light) 0%, #ffffff 100%);
            color: var(--text-light);
            transition: var(--transition);
        }

        body[data-theme='dark'] {
            background: linear-gradient(135deg, var(--bg-dark) 0%, #3a0ca3 100%);
            color: var(--text-dark);
        }

        /* Header styles */
        header {
            background: rgba(238, 160, 167, 0.5);
            backdrop-filter: blur(15px);
            border-bottom: 1px solid rgba(255, 255, 255, 0.15);
            padding: 1rem 2rem;
            position: sticky;
            top: 0;
            z-index: 100;
            box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
            transition: var(--transition);
        }

        header.scrolled {
            background: rgba(40, 10, 15, 0.8);
            box-shadow: 0 4px 25px rgba(0, 0, 0, 0.25);
        }

        .header-content {
            display: flex;
            justify-content: space-between;
            align-items: center;
            max-width: 1200px;
            margin: 0 auto;
        }

        .logo {
            display: flex;
            align-items: center;
            gap: 0.6rem;
            font-size: 1.8rem;
            font-weight: 800;
            background: orangered;
            background-size: 300% 300%;
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            animation: gradientMove 4s ease infinite;
            cursor: pointer;
            transition: transform var(--transition);
        }

        .logo i {
            font-size: 2rem;
          color: #d00000;
        }

        .logo:hover {
            transform: scale(1.08);
        }

        .header-controls {
            display: flex;
            align-items: center;
            gap: 1rem;
        }

        .theme-toggle {
            background: rgba(255, 107, 129, 0.3);
            border: none;
            border-radius: 50%;
            width: 45px;
            height: 45px;
            display: flex;
            justify-content: center;
            align-items: center;
            color: #ffffff;
            font-size: 1.3rem;
            cursor: pointer;
            transition: var(--transition);
            box-shadow: 0 0 8px rgba(255, 255, 255, 0.2);
        }

        .theme-toggle:hover {
            background: rgba(230, 57, 70, 0.6);
            transform: rotate(-10deg) scale(1.05);
            box-shadow: 0 0 12px var(--primary), 0 0 20px var(--secondary);
        }

        @keyframes gradientMove {
            0% { background-position: 0% 50%; }
            50% { background-position: 100% 50%; }
            100% { background-position: 0% 50%; }
        }

        body[data-theme='dark'] header {
            background: rgba(20, 10, 15, 0.8);
            border-bottom: 1px solid rgba(255, 255, 255, 0.1);
        }

        /* Navigation styles */
        .button-strip {
            background: #ffffff;
            padding: 0.8rem 0;
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
            border-bottom: 1px solid #eee;
            position: sticky;
            top: 68px;
            z-index: 100;
            overflow-x: auto;
            white-space: nowrap;
            -webkit-overflow-scrolling: touch; /* Smooth scrolling on iOS */
        }

        body[data-theme='dark'] .button-strip {
            background: rgba(23, 33, 49, 0.9);
            border-bottom-color: var(--border-dark);
        }

        .button-strip .container {
            display: inline-flex;
            gap: 0.5rem;
            padding: 0 1rem;
            align-items: center;
        }

        .qr-button {
            position: relative;
            background: rgba(230, 57, 70, 0.2);
            border: none;
            padding: 0.6rem 1.4rem;
            border-radius: 50px;
            font-size: 0.95rem;
            font-weight: 600;
            color: var(--text-light);
            display: inline-flex;
            align-items: center;
            gap: 0.5rem;
            cursor: pointer;
            transition: var(--transition);
            box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.05);
            white-space: nowrap;
            min-width: 120px;
            text-align: center;
        }

        body[data-theme='dark'] .qr-button {
            color: var(--text-dark);
        }

        .qr-button i {
            font-size: 1rem;
            opacity: 0.7;
            color: var(--accent);
        }

        .qr-button:hover {
            background: rgba(244, 140, 6, 0.3);
            transform: translateY(-2px);
        }

        .qr-button.active {
            background: linear-gradient(135deg, var(--primary), var(--secondary));
            color: #ffffff;
            box-shadow: 0 3px 10px rgba(230, 57, 70, 0.3);
        }

        .qr-button.active::after {
            content: '';
            position: absolute;
            bottom: -4px;
            left: 50%;
            transform: translateX(-50%);
            width: 20px;
            height: 4px;
            border-radius: 2px;
            background: var(--secondary);
            animation: bounce 1s infinite ease-in-out alternate;
        }

        @keyframes bounce {
            0% { transform: translateX(-50%) translateY(0); }
            100% { transform: translateX(-50%) translateY(-3px); }
        }

        /* Generator section */
        .generator-section {
            background: var(--card-light);
            padding: 2rem;
            margin: 2rem auto;
            border-radius: 16px;
            box-shadow: var(--shadow);
            border: 3px dotted var(--primary);
            max-width: 600px;
            text-align: center;
            transition: var(--transition);
        }

        body[data-theme='dark'] .generator-section {
            background: var(--card-dark);
            border-color: var(--border-dark);
        }

        .generator-section:hover {
            transform: translateY(-4px);
            box-shadow: var(--shadow-lg);
        }

        .generator-section h2 {
            margin-bottom: 2rem;
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 0.5rem;
            font-size: 1.6rem;
            font-weight: 700;
            background: linear-gradient(135deg, var(--primary), var(--secondary));
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
        }

        .generator-section h2 i {
            color: var(--accent);
            font-size: 1.4rem;
            transition: transform var(--transition);
        }

        .generator-section h2:hover i {
            transform: rotate(360deg);
        }

        .generator-form {
            display: flex;
            flex-direction: column;
            gap: 1rem;
        }

        .generator-form label {
            font-size: 0.9rem;
            font-weight: 500;
            text-align: left;
            color: var(--text-light);
        }

        body[data-theme='dark'] .generator-form label {
            color: var(--text-dark);
        }

        .generator-form input,
        .generator-form select {
            padding: 0.75rem 1rem;
            border: 2px solid var(--border-light);
            border-radius: 12px;
            background: var(--card-light);
            color: var(--text-light);
            font-size: 1rem;
            transition: var(--transition);
        }

        body[data-theme='dark'] .generator-form input,
        body[data-theme='dark'] .generator-form select {
            background: var(--card-dark);
            border-color: var(--border-dark);
            color: var(--text-dark);
        }

        .generator-form input:focus,
        .generator-form select:focus {
            outline: none;
            border-color: var(--primary);
            box-shadow: 0 0 0 3px rgba(230, 57, 70, 0.1);
        }

        .generate-btn {
            width: 100%;
            padding: 0.75rem 1rem;
            background: linear-gradient(135deg, var(--primary), var(--secondary));
            color: #fff;
            font-size: 1rem;
            font-weight: 600;
            border: none;
            border-radius: 8px;
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 0.5rem;
            cursor: pointer;
            box-shadow: 0 3px 6px rgba(0, 0, 0, 0.15);
            transition: var(--transition);
        }

        .generate-btn i {
            font-size: 1rem;
        }

        .generate-btn:hover {
            background: linear-gradient(135deg, var(--secondary), var(--primary));
            transform: translateY(-2px);
        }

        .generate-btn:active {
            transform: scale(0.98);
        }

        /* Customization panel */
        .customize-panel {
            background: var(--card-light);
            padding: 1.5rem;
            margin: 1rem auto;
            border-radius: 12px;
            box-shadow: var(--shadow);
            border: 2px dotted var(--primary);
            max-width: 600px;
            text-align: center;
            transition: var(--transition);
        }

        body[data-theme='dark'] .customize-panel {
            background: var(--card-dark);
            border-color: var(--border-dark);
        }

        .customize-panel h3 {
            font-size: 1.4rem;
            font-weight: 600;
            margin-bottom: 1rem;
            color: inherit; /* Use theme text color */
        }

        .customize-form {
            display: flex;
            flex-direction: column;
            gap: 1rem;
        }

        .customize-form label {
            font-size: 0.9rem;
            font-weight: 500;
            color: var(--text-light);
            text-align: left;
        }

        body[data-theme='dark'] .customize-form label {
            color: var(--text-dark);
        }

        .customize-form input[type="color"] {
            width: 100%;
            height: 18px;
            padding: 0;
            border: none;
            border-radius: 8px;
            cursor: pointer;
        }

        .customize-form select {
            width: 100%;
        }

        #qrCodeOutput {
            margin-top: 1.5rem;
            display: flex;
            flex-direction: column;
            align-items: center;
        }

        #qrCodeOutput canvas {
            border: 2px solid var(--border-light);
            border-radius: 8px;
            transition: var(--transition);
        }

        body[data-theme='dark'] #qrCodeOutput canvas {
            border-color: var(--border-dark);
        }

        .download-btn {
            margin-top: 1rem;
            padding: 0.5rem 1rem;
            background: linear-gradient(135deg, var(--accent), var(--secondary));
            color: #fff;
            font-size: 0.9rem;
            font-weight: 600;
            border: none;
            border-radius: 8px;
            display: flex;
            align-items: center;
            gap: 0.5rem;
            cursor: pointer;
            box-shadow: 0 3px 6px rgba(0, 0, 0, 0.15);
            transition: var(--transition);
            display: none; /* Hidden until QR is generated */
        }

        .download-btn:hover {
            background: linear-gradient(135deg, var(--secondary), var(--accent));
            transform: translateY(-2px);
        }

        .download-btn i {
            font-size: 1rem;
        }

        /* Responsive design */
        @media (max-width: 768px) {
            header {
                padding: 0.8rem 1rem;
            }

            .logo {
                font-size: 1.5rem;
            }

            .logo i {
                font-size: 1.7rem;
            }

            .theme-toggle {
                width: 40px;
                height: 40px;
                font-size: 1.1rem;
            }

            .button-strip {
                top: 58px; /* Adjusted for smaller header */
                padding: 0.5rem 0;
            }

            .button-strip .container {
                padding: 0 0.5rem;
                gap: 0.3rem;
            }

            .qr-button {
                padding: 0.5rem 1rem;
                font-size: 0.85rem;
                min-width: 100px;
            }

            .qr-button i {
                font-size: 0.9rem;
            }

            .generator-section,
            .customize-panel {
                padding: 1.5rem;
                margin: 1.5rem 1rem;
                max-width: 100%;
            }

            .generator-section h2 {
                font-size: 1.4rem;
            }

            .generator-form input,
            .generator-form select {
                font-size: 0.95rem;
            }

            .generate-btn {
                font-size: 0.95rem;
            }

            .customize-panel h3 {
                font-size: 1.2rem;
            }
        }

        @media (min-width: 769px) and (max-width: 1200px) {
            .generator-section,
            .customize-panel {
                max-width: 700px;
            }
        }

  .size-options button {
    padding: 0.5rem 1rem;
    margin-right: 5px;
    background: #9b8383; /* Grey for unselected buttons */
    color: #000000;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
}

.size-options button:disabled {
   background: linear-gradient(135deg, var(--secondary), var(--primary));/* Orange for selected button */
    cursor: default; /* No pointer for selected button */
}

.size-options button:hover:not(:disabled) {
   background: linear-gradient(135deg, var(--secondary), var(--primary)); /* Hover effect for unselected buttons */
    transform: translateY(-2px);
}