* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        :root {
            --primary: #6366f1;
            --primary-dark: #4f46e5;
            --primary-light: #818cf8;
            --secondary: #10b981;
            --danger: #ef4444;
            --warning: #f59e0b;
            --dark: #1e293b;
            --dark-light: #334155;
            --light: #f8fafc;
            --border: #e2e8f0;
            --text: #0f172a;
            --text-muted: #64748b;
            --shadow: rgba(0, 0, 0, 0.1);
            --bg-gradient-1: #000000;
            --bg-gradient-2: #000000;
        }

        [data-theme="dark"] {
            --primary: #818cf8;
            --primary-dark: #6366f1;
            --primary-light: #a5b4fc;
            --secondary: #34d399;
            --danger: #f87171;
            --warning: #fbbf24;
            --dark: #0f172a;
            --dark-light: #1e293b;
            --light: #0f172a;
            --border: #475569;
            --text: #f1f5f9;
            --text-muted: #cbd5e1;
            --shadow: rgba(0, 0, 0, 0.4);
            --bg-gradient-1: #0f172a;
            --bg-gradient-2: #020617;
        }

        body {
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
            background: linear-gradient(135deg, var(--bg-gradient-1) 0%, var(--bg-gradient-2) 100%);
            min-height: 100vh;
            display: flex;
            align-items: center;
            justify-content: center;
            padding: 20px;
            transition: background 0.3s ease, color 0.3s ease;
        }

        body::before {
            content: "";
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: radial-gradient(
                circle at 20% 50%,
                rgba(99, 102, 241, 0.3) 0%,
                transparent 50%
            ),
            radial-gradient(
                circle at 80% 80%,
                rgba(139, 92, 246, 0.3) 0%,
                transparent 50%
            ),
            radial-gradient(
                circle at 40% 20%,
                rgba(236, 72, 153, 0.2) 0%,
                transparent 50%
            );
            z-index: -2;
            animation: gradientShift 15s ease infinite;
        }

        [data-theme="dark"] body::before {
            background: radial-gradient(
                circle at 20% 50%,
                rgba(99, 102, 241, 0.15) 0%,
                transparent 50%
            ),
            radial-gradient(
                circle at 80% 80%,
                rgba(139, 92, 246, 0.15) 0%,
                transparent 50%
            ),
            radial-gradient(
                circle at 40% 20%,
                rgba(236, 72, 153, 0.1) 0%,
                transparent 50%
            );
        }

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

        .container {
            background: var(--light);
            border-radius: 20px;
            box-shadow: 0 20px 40px var(--shadow);
            padding: 40px;
            width: 100%;
            max-width: 500px;
            text-align: center;
            position: relative;
            animation: containerFadeIn 0.8s cubic-bezier(0.16, 1, 0.3, 1);
        }

        .header {
            margin-bottom: 30px;
        }

        .top-bar {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 20px;
        }

        .logo-section {
            display: flex;
            align-items: center;
            gap: 15px;
        }

        .logo {
            font-size: 1.5rem;
            font-weight: 700;
            color: var(--primary);
            letter-spacing: 1px;
        }

        .back-btn {
            color: var(--text-muted);
            text-decoration: none;
            font-size: 0.9rem;
            padding: 10px 16px;
            border-radius: 8px;
            transition: all 0.2s ease;
            border: 1px solid var(--border);
            font-weight: 500;
            display: flex;
            align-items: center;
            gap: 5px;
        }

        .back-btn:hover {
            color: var(--primary);
            border-color: var(--primary);
            background: rgba(99, 102, 241, 0.1);
            transform: translateX(-2px);
        }

        .theme-toggle {
            background: none;
            border: 2px solid var(--border);
            border-radius: 12px;
            padding: 10px 14px;
            font-size: 1.2rem;
            cursor: pointer;
            transition: all 0.3s ease;
            color: var(--text);
            display: flex;
            align-items: center;
            justify-content: center;
            min-width: 50px;
            min-height: 44px;
        }

        .theme-toggle:hover {
            border-color: var(--primary);
            background: rgba(99, 102, 241, 0.1);
            transform: scale(1.05);
        }

        .theme-toggle:active {
            transform: scale(0.95);
        }

        /* Responsive design */
        @media (max-width: 768px) {
            .container {
                padding: 25px 20px;
                max-width: 100%;
                margin: 10px;
            }

            .top-bar {
                flex-direction: column;
                gap: 15px;
                align-items: stretch;
            }

            .logo-section {
                justify-content: center;
                flex-wrap: wrap;
            }

            .theme-toggle {
                align-self: center;
                min-width: 60px;
            }

            .header h1 {
                font-size: 2.2rem;
            }

            .header p {
                font-size: 1rem;
            }

            .input-group {
                margin-bottom: 25px;
            }

            .email-input {
                padding: 16px 18px;
                font-size: 1rem;
            }

            .check-btn {
                padding: 16px 30px;
                font-size: 1rem;
            }

            .result {
                padding: 20px;
            }

            .result h3 {
                font-size: 1.2rem;
            }

            .examples {
                padding: 15px;
            }

            .example-list {
                grid-template-columns: 1fr;
                gap: 8px;
            }

            .example-btn {
                padding: 12px 16px;
                font-size: 0.85rem;
            }
        }

        @media (max-width: 480px) {
            .container {
                padding: 20px 15px;
            }

            .header h1 {
                font-size: 1.8rem;
            }

            .header p {
                font-size: 0.95rem;
            }

            .email-input {
                padding: 14px 16px;
                font-size: 0.95rem;
            }

            .check-btn {
                padding: 14px 25px;
                font-size: 0.95rem;
            }

            .result {
                padding: 18px;
                margin-top: 25px;
            }

            .result-icon {
                font-size: 1.8rem;
            }

            .result h3 {
                font-size: 1.1rem;
            }
        }

        .header h1 {
            color: var(--text);
            font-size: 2.5rem;
            margin-bottom: 10px;
            font-weight: 700;
        }

        .header p {
            color: var(--text-muted);
            font-size: 1.1rem;
        }

        .input-group {
            margin-bottom: 30px;
            position: relative;
        }

        .email-input {
            width: 100%;
            padding: 18px 20px;
            border: 2px solid var(--border);
            border-radius: 14px;
            font-size: 1.1rem;
            transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
            outline: none;
            background: var(--light);
            color: var(--text);
            position: relative;
        }

        .email-input:focus {
            border-color: var(--primary);
            box-shadow: 0 0 0 4px rgba(102, 126, 234, 0.15), 0 4px 12px rgba(102, 126, 234, 0.1);
            transform: translateY(-1px);
        }

        .email-input:valid {
            border-color: var(--secondary);
        }

        .email-input:invalid:not(:placeholder-shown) {
            border-color: var(--danger);
            box-shadow: 0 0 0 4px rgba(239, 68, 68, 0.15);
        }

        .check-btn {
            background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
            color: white;
            border: none;
            padding: 18px 40px;
            border-radius: 14px;
            font-size: 1.1rem;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
            width: 100%;
            margin-top: 15px;
            position: relative;
            overflow: hidden;
        }

        .check-btn::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
            transition: left 0.5s;
        }

        .check-btn:hover::before {
            left: 100%;
        }

        .check-btn:hover {
            transform: translateY(-3px);
            box-shadow: 0 12px 30px rgba(102, 126, 234, 0.4);
        }

        .check-btn:active {
            transform: translateY(-1px);
        }

        .check-btn:disabled {
            opacity: 0.6;
            cursor: not-allowed;
            transform: none;
            box-shadow: none;
        }

        .check-btn:disabled::before {
            display: none;
        }

        .docs-link {
            text-align: center;
            margin-bottom: 25px;
        }

        .btn-secondary {
            display: inline-flex;
            align-items: center;
            gap: 8px;
            color: var(--text-muted);
            text-decoration: none;
            padding: 12px 24px;
            border: 2px solid var(--border);
            border-radius: 12px;
            font-size: 0.95rem;
            font-weight: 500;
            transition: all 0.3s ease;
            background: var(--light);
        }

        .btn-secondary:hover {
            color: var(--primary);
            border-color: var(--primary);
            background: rgba(99, 102, 241, 0.05);
            transform: translateY(-2px);
            box-shadow: 0 6px 20px rgba(99, 102, 241, 0.15);
        }

        .result {
            margin-top: 30px;
            padding: 25px;
            border-radius: 16px;
            display: none;
            animation: slideIn 0.6s cubic-bezier(0.16, 1, 0.3, 1);
            position: relative;
            overflow: hidden;
        }

        .result::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            height: 4px;
            background: linear-gradient(90deg, transparent, rgba(255,255,255,0.3), transparent);
        }

        .result.success {
            background: linear-gradient(135deg, #10b981 0%, #059669 100%);
            color: white;
            box-shadow: 0 10px 30px rgba(16, 185, 129, 0.3);
        }

        .result.error {
            background: linear-gradient(135deg, #ef4444 0%, #dc2626 100%);
            color: white;
            box-shadow: 0 10px 30px rgba(239, 68, 68, 0.3);
        }

        .result.warning {
            background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%);
            color: white;
            box-shadow: 0 10px 30px rgba(245, 158, 11, 0.3);
        }

        .result-icon {
            font-size: 2rem;
            margin-bottom: 10px;
            display: block;
        }

        .result h3 {
            font-size: 1.4rem;
            margin-bottom: 8px;
            font-weight: 700;
            display: flex;
            align-items: center;
            gap: 10px;
        }

        .result p {
            font-size: 1rem;
            margin-bottom: 8px;
            opacity: 0.9;
        }

        .result-details {
            background: rgba(255, 255, 255, 0.1);
            padding: 15px;
            border-radius: 8px;
            margin-top: 15px;
            backdrop-filter: blur(10px);
        }

        .loading {
            display: inline-flex;
            align-items: center;
            justify-content: center;
            width: 24px;
            height: 24px;
            border: 3px solid rgba(255, 255, 255, 0.3);
            border-radius: 50%;
            border-top-color: white;
            animation: spin 1s linear infinite;
            margin-right: 12px;
        }

        @keyframes slideIn {
            from {
                opacity: 0;
                transform: translateY(30px) scale(0.95);
            }
            to {
                opacity: 1;
                transform: translateY(0) scale(1);
            }
        }

        @keyframes shake {
            0%, 100% { transform: translateX(0); }
            10%, 30%, 50%, 70%, 90% { transform: translateX(-5px); }
            20%, 40%, 60%, 80% { transform: translateX(5px); }
        }

        @keyframes spin {
            to { transform: rotate(360deg); }
        }

        .examples {
            margin-top: 25px;
            text-align: left;
            padding: 20px;
            background: rgba(99, 102, 241, 0.03);
            border-radius: 12px;
            border: 1px solid var(--border);
        }

        .examples h4 {
            color: var(--text);
            margin-bottom: 15px;
            font-size: 1rem;
            font-weight: 600;
            display: flex;
            align-items: center;
            gap: 8px;
        }

        .examples h4::before {
            content: '💡';
            font-size: 1.2rem;
        }

        .example-list {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 10px;
        }

        .example-btn {
            background: var(--light);
            border: 1px solid var(--border);
            padding: 10px 14px;
            border-radius: 10px;
            font-size: 0.9rem;
            cursor: pointer;
            transition: all 0.3s ease;
            color: var(--text-muted);
            text-align: center;
            font-family: 'Monaco', 'Menlo', 'Ubuntu Mono', monospace;
            position: relative;
            overflow: hidden;
        }

        .example-btn::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(99, 102, 241, 0.1), transparent);
            transition: left 0.4s;
        }

        .example-btn:hover::before {
            left: 100%;
        }

        .example-btn:hover {
            background: var(--primary);
            color: white;
            border-color: var(--primary);
            transform: translateY(-2px);
            box-shadow: 0 4px 15px rgba(99, 102, 241, 0.2);
        }