:root {
            --primary: #6366f1;
            --primary-dark: #4f46e5;
            --success: #10b981;
            --text: #1e293b;
            --text-muted: #64748b;
            --border: #e2e8f0;
        }

        * {
            box-sizing: border-box;
        }

        body {
            font-family: 'Noto Sans JP', -apple-system, BlinkMacSystemFont, sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            display: flex;
            flex-direction: column;
            justify-content: center;
            align-items: center;
            min-height: 100vh;
            margin: 0;
            padding: 20px;
        }

        .login-card {
            background: white;
            padding: 45px 40px;
            border-radius: 24px;
            box-shadow: 0 25px 80px rgba(0, 0, 0, 0.25);
            width: 100%;
            max-width: 420px;
            text-align: center;
            animation: cardPop 0.4s ease-out;
        }

        @keyframes cardPop {
            from {
                opacity: 0;
                transform: scale(0.95) translateY(15px);
            }

            to {
                opacity: 1;
                transform: scale(1) translateY(0);
            }
        }

        .logo {
            font-size: 1.8rem;
            font-weight: 800;
            color: var(--primary);
            margin-bottom: 8px;
        }

        .subtitle {
            color: var(--text-muted);
            font-size: 0.95rem;
            margin-bottom: 30px;
        }

        input {
            width: 100%;
            padding: 14px 18px;
            margin-bottom: 15px;
            border: 2px solid var(--border);
            border-radius: 12px;
            font-size: 1rem;
            font-family: inherit;
            transition: all 0.2s;
            background: #f8fafc;
        }

        input:focus {
            outline: none;
            border-color: var(--primary);
            background: white;
            box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.1);
        }

        button {
            width: 100%;
            padding: 14px;
            border: none;
            border-radius: 12px;
            font-weight: 700;
            font-size: 1rem;
            cursor: pointer;
            transition: all 0.2s;
            font-family: inherit;
        }

        .btn-primary {
            background: linear-gradient(135deg, var(--primary) 0%, #8b5cf6 100%);
            color: white;
            margin-bottom: 12px;
            box-shadow: 0 4px 15px rgba(99, 102, 241, 0.3);
        }

        .btn-primary:hover {
            transform: translateY(-2px);
            box-shadow: 0 6px 20px rgba(99, 102, 241, 0.4);
        }

        .btn-success {
            background: linear-gradient(135deg, var(--success) 0%, #059669 100%);
            color: white;
            box-shadow: 0 4px 15px rgba(16, 185, 129, 0.3);
        }

        .btn-success:hover {
            transform: translateY(-2px);
            box-shadow: 0 6px 20px rgba(16, 185, 129, 0.4);
        }

        .btn-google {
            background: white;
            color: #757575;
            border: 1px solid var(--border);
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 10px;
            box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
        }

        .btn-google:hover {
            background: #f8fafc;
            transform: translateY(-2px);
            box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
        }

        .btn-google img {
            width: 18px;
            height: 18px;
        }

        .error {
            color: #ef4444;
            font-size: 0.85rem;
            margin-top: 15px;
            padding: 10px;
            background: #fef2f2;
            border-radius: 8px;
            display: none;
        }

        .error:not(:empty) {
            display: block;
        }

        .back-link {
            display: block;
            margin-top: 25px;
            color: var(--text-muted);
            text-decoration: none;
            font-size: 0.9rem;
            transition: color 0.2s;
        }

        .back-link:hover {
            color: var(--primary);
        }

        .divider {
            display: flex;
            align-items: center;
            margin: 20px 0;
            color: var(--text-muted);
            font-size: 0.85rem;
        }

        .divider::before,
        .divider::after {
            content: '';
            flex: 1;
            height: 1px;
            background: var(--border);
        }

        .divider::before {
            margin-right: 15px;
        }

        .divider::after {
            margin-left: 15px;
        }

        .tab-container {
            display: flex;
            margin-bottom: 20px;
            background: #f1f5f9;
            border-radius: 12px;
            padding: 4px;
        }

        .tab-btn {
            flex: 1;
            background: transparent;
            color: var(--text-muted);
            padding: 10px;
            border-radius: 10px;
            font-weight: 700;
            font-size: 0.95rem;
            border: none;
            box-shadow: none;
        }

        .tab-btn.active {
            background: white;
            color: var(--primary);
            box-shadow: 0 2px 5px rgba(0, 0, 0, 0.05);
        }

        .tab-btn:hover:not(.active) {
            color: var(--text);
        }

        .form-section {
            display: none;
            animation: fadeIn 0.3s ease;
        }

        .form-section.active {
            display: block;
        }

        @keyframes fadeIn {
            from {
                opacity: 0;
                transform: translateY(5px);
            }

            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        @media (max-width: 480px) {
            .login-card {
                padding: 35px 25px;
            }

            .logo {
                font-size: 1.5rem;
            }
        }