html, body {
            margin: 0;
            padding: 0;
        }
        *, *:before, *:after {
            box-sizing: border-box;
        }
        html {
            scroll-behavior: smooth;
        }

        body {
            font-family: 'Noto Sans JP', sans-serif;
            background-color: #f8f7f4; /* Warm Neutral Background */
            color: #3a3a3a;
            -webkit-font-smoothing: antialiased;
            -moz-osx-font-smoothing: grayscale;
        }
        a {
            text-decoration: none;
        }
        .main-cta-button {
            background-color: #2dd4bf; /* Teal */
            transition: all 0.2s;
        }
        .main-cta-button:hover {
            background-color: #0f766e; /* Darker Teal */
            box-shadow: 0 4px 15px rgba(45, 212, 191, 0.5);
        }
        .tab-active {
            border-bottom: 3px solid #2dd4bf;
            color: #2dd4bf;
            font-weight: 700;
        }
        /* Mobile-first: Ensure content grid is responsive */
        #stampGrid > div {
            min-height: 150px; 
        }

        /* Header Styles */
        .header {
            position: sticky;
            top: 0;
            z-index: 50;
            background-color: #fff;
            box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
        }
        .header-container {
            max-width: 56rem;
            margin-left: auto;
            margin-right: auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
            height: 4rem;
            padding-left: 1rem;
            padding-right: 1rem;
        }
        .header-title {
            font-size: 1.5rem;
            line-height: 2rem;
            font-weight: 700;
            color: #0d9488;
        }
        .header-cta {
            color: #fff;
            padding-left: 1rem;
            padding-right: 1rem;
            padding-top: 0.25rem;
            padding-bottom: 0.25rem;
            border-radius: 9999px;
            font-size: 0.875rem;
            line-height: 1.25rem;
            font-weight: 600;
            box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
        }

        /* Main Content */
        .main-content {
            max-width: 56rem;
            margin-left: auto;
            margin-right: auto;
            padding: 1rem;
            padding-top: 2rem;
        }

        /* Hero Section */
        .hero-section {
            text-align: center;
            margin-bottom: 3rem;
        }
        .hero-title {
            font-size: 1.875rem;
            line-height: 2.25rem;
            font-weight: 800;
            color: #1f2937;
            margin-bottom: 1rem;
            line-height: 1.25;
        }
        @media (min-width: 640px) {
            .hero-title {
                font-size: 2.25rem;
                line-height: 2.5rem;
            }
        }
        .hero-subtitle {
            color: #0d9488;
        }
        .hero-image-grid {
            margin-top: 1.5rem;
            margin-bottom: 1.5rem;
            display: grid;
            grid-template-columns: repeat(3, minmax(0, 1fr));
            gap: 1rem;
        }
        .hero-cta {
            color: #fff;
            padding: 0.75rem 2rem;
            border-radius: 0.75rem;
            font-size: 1.25rem;
            line-height: 1.75rem;
            font-weight: 700;
            box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
            display: inline-block;
            transition-property: transform;
        }
        .hero-cta:hover {
            transform: scale(1.05);
        }

        /* Features Section */
        .features-section {
            margin-bottom: 3rem;
        }
        .features-title {
            font-size: 1.25rem;
            line-height: 1.75rem;
            font-weight: 700;
            color: #374151;
            margin-bottom: 1.5rem;
            border-bottom-width: 1px;
            padding-bottom: 0.5rem;
        }
        .features-grid {
            display: grid;
            grid-template-columns: repeat(1, minmax(0, 1fr));
            gap: 1.5rem;
        }
        @media (min-width: 640px) {
            .features-grid {
                grid-template-columns: repeat(3, minmax(0, 1fr));
            }
        }
        .feature-card {
            background-color: #fff;
            padding: 1.25rem;
            border-radius: 0.75rem;
            box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
            text-align: center;
        }
        .feature-icon {
            margin-left: auto;
            margin-right: auto;
            margin-bottom: 0.5rem;
            width: 30%;
        }
        .feature-card-title {
            font-weight: 700;
            font-size: 1.125rem;
            line-height: 1.75rem;
            color: #0f766e;
        }
        .feature-image-grid {
            display: grid;
            grid-template-columns: repeat(3, minmax(0, 1fr));
            gap: 0.5rem;
        }

        /* Stamps Section */
        .stamps-section {
            margin-bottom: 3rem;
            background-color: #fff;
            padding: 1rem;
            border-radius: 0.75rem;
            box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
        }
        .stamps-title {
            font-size: 1.5rem;
            line-height: 2rem;
            font-weight: 700;
            color: #1f2937;
            margin-bottom: 1rem;
        }
        .stamp-grid {
            display: grid;
            grid-template-columns: repeat(3, minmax(0, 1fr));
            gap: 0.75rem;
        }
        .stamp-card {
            background-color: #f3f4f6;
            padding: 0.5rem;
            border-radius: 0.75rem;
            box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            cursor: pointer;
            transition-property: transform;
            transition-duration: 200ms;
            position: relative;
        }
        .stamp-card:hover {
            transform: scale(1.05);
        }
        .stamp-image {
            width: 100%;
            height: auto;
            border-radius: 0.375rem;
        }
        .stamp-title {
            font-size: 0.875rem;
            line-height: 1.25rem;
            font-weight: 500;
            color: #374151;
            text-align: center;
            line-height: 1.25;
            margin-top: 0.5rem;
        }
        .stamp-gif-badge {
            position: absolute;
            top: 0.25rem;
            right: 0.25rem;
            font-size: 0.75rem;
            line-height: 1rem;
            background-color: #f87171;
            color: #fff;
            padding-left: 0.25rem;
            padding-right: 0.25rem;
            border-radius: 9999px;
        }
        .stamps-cta-container {
            text-align: center;
            margin-top: 2rem;
            margin-bottom: 2rem;
        }
        .stamps-cta {
            color: #fff;
            padding: 0.5rem 1.5rem;
            border-radius: 9999px;
            font-weight: 600;
            box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
        }

        /* Pricing Section */
        .pricing-section {
            margin-bottom: 3rem;
            background-color: #f0fdfa;
            padding: 1.5rem;
            border-radius: 0.75rem;
            box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
            text-align: center;
            border: 1px solid #a7f3d0;
        }
        .pricing-title {
            font-size: 1.875rem;
            line-height: 2.25rem;
            font-weight: 700;
            color: #134e4a;
            margin-bottom: 1rem;
        }
        .price {
            font-size: 3rem;
            line-height: 1;
            font-weight: 800;
            color: #0d9488;
            margin-bottom: 0.5rem;
        }
        .price-period {
            font-size: 1.25rem;
            line-height: 1.75rem;
            font-weight: 400;
        }
        .pricing-description {
            color: #374151;
            margin-bottom: 1.5rem;
        }
        .pricing-cta {
            color: #fff;
            padding: 0.75rem 2rem;
            border-radius: 0.75rem;
            font-size: 1.25rem;
            line-height: 1.75rem;
            font-weight: 700;
            box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
            display: inline-block;
            transition-property: transform;
        }
        .pricing-cta:hover {
            transform: scale(1.05);
        }
        .download-message {
            margin-top: 1rem;
            padding: 0.75rem;
            background-color: #fee2e2;
            color: #b91c1c;
            border-radius: 0.5rem;
            font-weight: 500;
            box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
            margin-left: auto;
            margin-right: auto;
            max-width: 24rem;
        }
        .hidden {
            display: none;
        }

        /* Usage Section */
        .usage-section {
            margin-bottom: 3rem;
        }
        .usage-title {
            font-size: 1.5rem;
            line-height: 2rem;
            font-weight: 700;
            color: #1f2937;
            margin-bottom: 1.5rem;
        }
        .usage-grid {
            display: grid;
            grid-template-columns: repeat(1, minmax(0, 1fr));
            gap: 1.5rem;
            text-align: center;
        }
        @media (min-width: 640px) {
            .usage-grid {
                grid-template-columns: repeat(3, minmax(0, 1fr));
            }
        }
        .usage-card {
            background-color: #fff;
            padding: 1.25rem;
            border-radius: 0.75rem;
            box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
        }
        .usage-card-icon {
            font-size: 2.25rem;
            line-height: 2.5rem;
            color: #0d9488;
            display: block;
            margin-bottom: 0.5rem;
        }
        .usage-card-title {
            font-weight: 700;
            font-size: 1.125rem;
            line-height: 1.75rem;
            margin-bottom: 0.25rem;
        }
        .usage-card-description {
            font-size: 0.875rem;
            line-height: 1.25rem;
            color: #4b5563;
        }

        /* Footer */
        .footer {
            background-color: #fff;
            border-top: 1px solid #e5e7eb;
            margin-top: 2.5rem;
        }
        .footer-container {
            max-width: 56rem;
            margin-left: auto;
            margin-right: auto;
            padding: 2rem 1rem;
            text-align: center;
            font-size: 0.875rem;
            line-height: 1.25rem;
            color: #6b7280;
        }
        .footer-text a {
            color: #2dd4bf;
        }
        .grid-image {
            width: 100%;
            height: auto;
            display: block;
        }

        /* Tab Navigation */
        .tab-nav {
            display: flex;
            overflow-x: auto;
            white-space: nowrap;
            border-bottom: 1px solid #e5e7eb;
            margin-bottom: 1rem;
            gap: 1rem; /* Add some space between tabs */
        }

        .tab-link {
            padding: 0.5rem 1rem;
            cursor: pointer;
            border: none;
            background-color: transparent;
            font-size: 1rem;
            color: #6b7280;
            transition: all 0.2s;
            flex-shrink: 0; /* Prevent tabs from shrinking */
        }

        .tab-link.active {
            border-bottom: 3px solid #2dd4bf;
            color: #2dd4bf;
            font-weight: 700;
        }

        /* Tab Content */
        .tab-content {
            display: none;
        }

        .tab-content.active {
            display: block;
        }

        /* User Menu Section */
        .user-menu-section {
            margin-bottom: 3rem;
            text-align: center;
        }
        .user-menu-title {
            font-size: 1.5rem;
            line-height: 2rem;
            font-weight: 700;
            color: #1f2937;
            margin-bottom: 1.5rem;
        }
        .user-menu-grid {
            display: grid;
            grid-template-columns: repeat(2, minmax(0, 1fr));
            gap: 1rem;
        }
        @media (min-width: 640px) {
            .user-menu-grid {
                grid-template-columns: repeat(4, minmax(0, 1fr));
            }
        }
        .user-menu-link {
            background-color: #fff;
            padding: 1rem;
            border-radius: 0.75rem;
            box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
            color: #374151;
            font-weight: 600;
            transition: all 0.2s;
        }
        .user-menu-link:hover {
            background-color: #f3f4f6;
            color: #1f2937;
        }

        /* Genre List Section */
        .genre-list-section {
            margin-bottom: 3rem;
            text-align: center;
        }
        .genre-list-title {
            font-size: 1.5rem;
            line-height: 2rem;
            font-weight: 700;
            color: #1f2937;
            margin-bottom: 1.5rem;
        }
        .genre-list-grid {
            display: grid;
            grid-template-columns: repeat(2, minmax(0, 1fr));
            gap: 1rem;
        }
        @media (min-width: 640px) {
            .genre-list-grid {
                grid-template-columns: repeat(4, minmax(0, 1fr));
            }
        }
        .genre-list-link {
            background-color: #fff;
            padding: 1rem;
            border-radius: 0.75rem;
            box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
            color: #374151;
            font-weight: 600;
            transition: all 0.2s;
        }
        .genre-list-link:hover {
            background-color: #f3f4f6;
            color: #1f2937;
        }