:root {
            --color-bg: #f6f6f6;
            --color-surface: #ffffff;
            --color-text: #1f1f1f;
            --color-border: #dedede;
            --color-shadow: rgba(0, 0, 0, 0.08);
            -webkit-user-drag: none;
        }

        body {
            -webkit-user-drag: none;
            background-color: var(--color-bg);
            color: var(--color-text);
            -webkit-font-smoothing: antialiased;
            word-break: keep-all;
            overflow-x: hidden;
        }

        /* Scroll Animation */
        .reveal {
            opacity: 0;
            transform: translateY(30px);
            transition: all 0.8s cubic-bezier(0.16, 1, 0.3, 1);
        }

        .reveal.active {
            opacity: 1;
            transform: translateY(0);
        }

        .floating-element {
            animation: none;
        }

        .floating-delay {
            animation-delay: -3s;
        }

        .platform-switcher {
            margin-top: 18px;
            text-align: center;
        }

        .platform-helper-text {
            color: #6f6f6f;
            font-size: 0.95rem;
            margin-bottom: 10px;
            transition: opacity 0.2s ease, transform 0.2s ease;
        }

        #download-btn,
        #ios-development-notice {
            transition: opacity 0.22s cubic-bezier(0.16, 1, 0.3, 1), transform 0.22s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.22s ease;
        }

        #download-btn.platform-transitioning,
        #ios-development-notice.platform-transitioning,
        .platform-helper-text.platform-transitioning {
            opacity: 0;
            transform: translateY(5px) scale(0.985);
        }

        .platform-selector-buttons {
            display: inline-flex;
            gap: 8px;
            flex-wrap: wrap;
            justify-content: center;
        }

        .platform-selector-buttons button {
            border: 1px solid var(--color-border);
            background: var(--color-surface);
            color: var(--color-text);
            border-radius: 999px;
            padding: 8px 14px;
            font-weight: 700;
            transition: background-color 0.18s ease, border-color 0.18s ease, transform 0.18s ease;
        }

        .platform-selector-buttons button:hover,
        .platform-selector-buttons button:focus-visible {
            border-color: #fee500;
            transform: translateY(-1px);
        }

        .platform-selector-buttons button.active {
            background: #fee500;
            border-color: #fee500;
        }

        @media (prefers-reduced-motion: reduce) {
            #download-btn,
            #ios-development-notice,
            .platform-helper-text,
            .platform-selector-buttons button {
                transition: none;
            }
        }

        /* Mockup Windows Container */
        .mockup-container {
            position: relative;
            width: 100%;
            height: 680px;
            display: flex;
            justify-content: center;
            align-items: center;
            overflow: visible;
        }

        .mockup-ambient {
            position: absolute;
            inset: 5% 0 8% 4%;
            border-radius: 44px;
            background: radial-gradient(circle at 30% 22%, rgba(254, 229, 0, 0.2), transparent 34%), linear-gradient(135deg, rgba(255, 251, 219, 0.9), rgba(31, 31, 31, 0.035));
            border: 1px solid rgba(31, 31, 31, 0.06);
        }

        .window-frame {
            background: #fff;
            border-radius: 30px;
            box-shadow: 0 28px 70px -28px rgba(31, 31, 31, 0.28), 0 0 0 1px rgba(31, 31, 31, 0.07);
            overflow: hidden;
            position: absolute;
            display: flex;
            flex-direction: column;
            transition: transform 0.3s ease;
        }

        /* Main Window (List) Position */
        .main-window {
            width: 342px;
            height: 560px;
            z-index: 10;
            left: 50%;
            transform: translateX(-108%) translateY(14px) scale(0.98);
            opacity: 0.96;
        }

        /* Chat Window (Conversation) Position */
        .chat-window {
            width: 462px;
            height: 610px;
            z-index: 20;
            left: 50%;
            transform: translateX(-30%);
        }

        @media (max-width: 1024px) {
            .mockup-container {
                height: 620px;
            }

            .main-window {
                transform: translateX(-66%) translateY(18px) scale(0.88);
                opacity: 0.72;
            }

            .chat-window {
                transform: translateX(-38%) scale(0.9);
            }
        }

        @media (max-width: 640px) {
            .main-window {
                display: none;
            }

            .chat-window {
                position: relative;
                left: auto;
                transform: none;
                width: 100%;
                max-width: 360px;
                height: 560px;
            }
        }

        /* Window Controls */
        .window-titlebar {
            background: rgba(255, 255, 255, 0.94);
            height: 46px;
            display: flex;
            align-items: center;
            padding: 0 16px;
            border-bottom: 1px solid var(--color-border);
            flex-shrink: 0;
            position: relative;
            z-index: 10;
        }

        .window-title {
            font-size: 0.95rem;
            font-weight: 600;
            color: #111827;
            flex: 1;
        }

        .window-controls {
            margin-left: auto;
            display: inline-flex;
            gap: 6px;
            flex-shrink: 0;
        }

        .window-btn {
            width: 26px;
            height: 26px;
            border-radius: 9px;
            border: 1px solid rgba(15, 23, 42, 0.08);
            background: rgba(255, 255, 255, 0.85);
            color: #111827;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            font-size: 0.72rem;
            font-weight: 600;
            cursor: default;
            line-height: 1;
        }

        .window-btn.close {
            color: #ef4444;
            border-color: rgba(239, 68, 68, 0.3);
        }

        /* Sidebar Styles */
        .sidebar-content {
            flex: 1;
            background: #ffffff;
            padding: 16px;
            display: flex;
            flex-direction: column;
            gap: 12px;
            overflow: hidden;
        }

        /* My Profile Row */
        .my-profile {
            display: flex !important;
            flex-direction: row !important;
            align-items: center;
            gap: 12px;
            padding: 8px;
            margin-bottom: 4px;
            flex-wrap: nowrap !important;
        }

        .avatar {
            width: 60px;
            height: 60px;
            border-radius: 20px;
            background-color: #f3f4f6;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 32px;
            border: 1px solid #dedede;
            flex-shrink: 0;
        }

        .profile-avatar-surface {
            background: #fff8c7;
            border-color: rgba(31, 31, 31, 0.08);
            box-shadow: inset 0 0 0 1px rgba(254, 229, 0, 0.45);
        }

        .avatar-logo {
            width: 42px;
            height: 42px;
            display: block;
            object-fit: contain;
        }

        .friend-code-preview {
            display: flex;
            align-items: center;
            justify-content: space-between;
            padding: 10px 12px;
            border-radius: 16px;
            background: #fffdf0;
            border: 1px solid rgba(31, 31, 31, 0.06);
            font-size: 12px;
            color: #6f6f6f;
        }

        .friend-code-preview strong {
            color: #1f1f1f;
            font-size: 13px;
            letter-spacing: 0.04em;
        }

        .tab-bar {
            display: flex;
            gap: 4px;
            margin-bottom: 2px;
        }

        .tab-btn {
            flex: 1;
            text-align: center;
            padding: 8px 0;
            font-size: 12px;
            font-weight: 600;
            color: #6f6f6f;
            border-radius: 12px;
            border: 1px solid transparent;
            background: #f4f4ef;
        }

        .tab-btn.active {
            background: #fff;
            color: #1f1f1f;
            border-color: #fee500;
            box-shadow: inset 0 0 0 1px rgba(0, 0, 0, 0.04);
        }

        .preview-search-row {
            display: grid;
            grid-template-columns: minmax(0, 1fr) auto auto;
            gap: 8px;
            align-items: center;
            margin-bottom: 0;
        }

        .preview-search-field {
            min-width: 0;
            height: 38px;
            display: flex;
            align-items: center;
            padding: 0 12px;
            border-radius: 12px;
            border: 1px solid #dedede;
            background: #ffffff;
            color: #9ca3af;
            font-size: 12px;
            white-space: nowrap;
            overflow: hidden;
            text-overflow: ellipsis;
        }

        .preview-search-btn {
            height: 38px;
            padding: 0 12px;
            border-radius: 12px;
            background: #f4f4ef;
            color: #1f1f1f;
            font-size: 12px;
            font-weight: 700;
            border: 1px solid #dedede;
        }

        .preview-add-btn {
            width: 38px;
            height: 38px;
            border-radius: 999px;
            border: 1px solid #dedede;
            background: #fee500;
            color: #1f1f1f;
            font-size: 18px;
            font-weight: 700;
            line-height: 1;
            display: inline-flex;
            align-items: center;
            justify-content: center;
        }

        .preview-add-btn svg {
            width: 17px;
            height: 17px;
            stroke: currentColor;
            stroke-width: 2.2;
            stroke-linecap: round;
        }

        .preview-list-surface {
            display: flex;
            flex-direction: column;
            gap: 6px;
            padding: 8px;
            border-radius: 24px;
            border: 1px solid rgba(31, 31, 31, 0.07);
            background: #f7f7f2;
            box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.85);
            min-height: 0;
            overflow: hidden;
        }

        /* Chat List Item Layout */
        .list-item {
            display: flex !important;
            flex-direction: row !important;
            flex-wrap: nowrap !important;
            align-items: center !important;
            gap: 12px;
            padding: 11px;
            border-radius: 18px;
            background: #fff;
            border: 1px solid transparent;
            position: relative;
            width: 100%;
            box-sizing: border-box;
        }

        .list-item.active {
            border-color: rgba(254, 229, 0, 0.75);
            box-shadow: 0 10px 22px rgba(31, 31, 31, 0.06);
        }

        .list-avatar {
            width: 52px;
            height: 52px;
            border-radius: 18px;
            background-color: #e5e7eb;
            flex-shrink: 0;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 24px;
        }

        .list-avatar-stack,
        .chat-header-avatar {
            position: relative;
            overflow: hidden;
            background: #f7f7f2;
        }

        .chat-header-avatar {
            width: 40px;
            height: 40px;
            border-radius: 14px;
            border: 1px solid #dedede;
            flex-shrink: 0;
        }

        .chat-header-avatar.compact .list-avatar-dot {
            border-width: 1.5px;
        }

        .list-avatar-dot {
            position: absolute;
            width: 54%;
            height: 54%;
            border-radius: 50%;
            border: 2px solid #ffffff;
            box-shadow: 0 6px 14px rgba(31, 31, 31, 0.12);
        }

        .list-avatar-dot.slot-1 {
            top: 7%;
            left: 50%;
            transform: translateX(-50%);
        }

        .list-avatar-dot.slot-2 {
            left: 7%;
            bottom: 7%;
        }

        .list-avatar-dot.slot-3 {
            right: 7%;
            bottom: 7%;
        }

        .person-silhouette {
            position: relative;
            overflow: hidden;
        }

        .person-silhouette::before,
        .person-silhouette::after {
            content: '';
            position: absolute;
            left: 50%;
            transform: translateX(-50%);
            background: rgba(31, 31, 31, 0.42);
        }

        .person-silhouette::before {
            top: 12px;
            width: 16px;
            height: 16px;
            border-radius: 50%;
        }

        .person-silhouette::after {
            bottom: 10px;
            width: 28px;
            height: 18px;
            border-radius: 16px 16px 10px 10px;
        }

        .tone-yellow { background: #fee500; }
        .tone-blue { background: #dbeafe; }
        .tone-green { background: #dcfce7; }
        .tone-purple { background: #ede9fe; }

        .message-avatar,
        .message-avatar-spacer {
            width: 32px;
            height: 32px;
            border-radius: 12px;
            flex-shrink: 0;
            margin-top: 4px;
        }

        .message-avatar {
            border: 1px solid rgba(31, 31, 31, 0.08);
        }

        .message-avatar::before {
            top: 7px;
            width: 10px;
            height: 10px;
        }

        .message-avatar::after {
            bottom: 6px;
            width: 18px;
            height: 12px;
            border-radius: 12px 12px 7px 7px;
        }

        .list-content-wrapper {
            flex: 1;
            min-width: 0;
            display: flex;
            flex-direction: row !important;
            align-items: center !important;
            justify-content: space-between;
        }

        .list-text-group {
            flex: 1;
            min-width: 0;
            display: flex;
            flex-direction: column;
            justify-content: center;
            gap: 4px;
            margin-right: 8px;
        }

        .list-name {
            font-size: 0.95rem;
            font-weight: 600;
            color: #111827;
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
            text-align: left;
            line-height: 1.2;
        }

        .list-preview {
            font-size: 0.82rem;
            color: #6b7280;
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
            text-align: left;
            line-height: 1.2;
        }

        .list-meta-group {
            display: flex;
            flex-direction: row !important;
            align-items: center !important;
            gap: 8px;
            flex-shrink: 0;
        }

        .unread-badge {
            background-color: #ef4444;
            color: white;
            font-size: 11px;
            font-weight: 700;
            padding: 2px 6px;
            border-radius: 999px;
            min-width: 18px;
            text-align: center;
            line-height: 1.2;
        }

        .list-time {
            font-size: 11px;
            color: #9ca3af;
            white-space: nowrap;
            line-height: 1.2;
        }

        /* Chat Window Styles */
        .chat-window-content {
            flex: 1;
            display: flex;
            flex-direction: column;
            background: #fff;
            height: 100%;
            overflow: hidden;
            position: relative;
        }

        .chat-header {
            height: 68px;
            padding: 0 22px;
            display: flex;
            align-items: center;
            border-bottom: 1px solid var(--color-border);
            justify-content: space-between;
            flex-shrink: 0;
        }

        .header-actions {
            display: flex;
            gap: 8px;
            margin-left: auto;
        }

        .btn-light-small {
            border: 1px solid rgba(31, 31, 31, 0.08);
            background: #f7f7f2;
            color: #4b5563;
            width: 34px;
            height: 34px;
            padding: 0;
            border-radius: 13px;
            font-size: 0.8rem;
            font-weight: 600;
            display: inline-flex;
            align-items: center;
            justify-content: center;
        }

        .btn-light-small svg {
            width: 16px;
            height: 16px;
            fill: none;
            stroke: currentColor;
            stroke-width: 2;
            stroke-linecap: round;
            stroke-linejoin: round;
        }

        .btn-danger-small {
            border: 1px solid rgba(239, 68, 68, 0.32);
            background: rgba(239, 68, 68, 0.12);
            color: #b91c1c;
            padding: 6px 12px;
            border-radius: 999px;
            font-size: 0.8rem;
            font-weight: 600;
        }

        .chat-messages {
            flex: 1;
            padding: 22px;
            display: flex;
            flex-direction: column;
            gap: 16px;
            overflow-y: auto;
            background: linear-gradient(180deg, #fbfbf8 0%, #f4f4ef 100%);
            min-height: 0;
        }

        .bubble-row {
            display: flex;
            flex-direction: column;
            max-width: 75%;
        }

        .bubble-row.mine {
            align-self: flex-end;
            align-items: flex-end;
        }

        .bubble-row.theirs {
            align-self: flex-start;
            align-items: flex-start;
        }

        .bubble {
            padding: 10px 14px;
            border-radius: 20px;
            font-size: 14px;
            line-height: 1.45;
            box-shadow: 0 8px 22px rgba(31, 31, 31, 0.05);
        }

        .bubble.mine {
            background-color: #fee500;
            color: #1f1f1f;
            border-bottom-right-radius: 4px;
        }

        .bubble.theirs {
            background-color: #ffffff;
            border: 1px solid rgba(0, 0, 0, 0.05);
            border-bottom-left-radius: 4px;
        }

        .chat-input-bar {
            padding: 14px 22px 18px;
            border-top: 1px solid var(--color-border);
            background: #fff;
            display: flex;
            flex-direction: column;
            gap: 10px;
            flex-shrink: 0;
            width: 100%;
        }

        .chat-input-main {
            display: flex;
            align-items: flex-start;
            gap: 10px;
        }

        .attachment-toggle-btn {
            width: 44px;
            height: 44px;
            border-radius: 16px;
            border: 1px solid #dedede;
            background: #f7f7f2;
            color: #1f1f1f;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 20px;
            font-weight: 700;
            flex-shrink: 0;
            cursor: pointer;
        }

        .image-preview-card {
            width: 206px;
            height: 128px;
            background: #eef0ea;
            position: relative;
            overflow: hidden;
        }

        .image-preview-sky {
            position: absolute;
            inset: 14px 16px 34px;
            border-radius: 14px;
            background: linear-gradient(160deg, #dce7f2, #f7e7b6 62%, #b9c7a4);
        }

        .image-preview-caption {
            position: absolute;
            left: 14px;
            right: 14px;
            bottom: 12px;
            color: #6b7280;
            font-size: 11px;
            font-weight: 600;
        }

        .feature-mark {
            width: 52px;
            height: 52px;
            border-radius: 18px;
            background: #ffffff;
            border: 1px solid rgba(31, 31, 31, 0.08);
            display: flex;
            align-items: center;
            justify-content: center;
            color: #1f1f1f;
            box-shadow: 0 8px 18px rgba(31, 31, 31, 0.05);
            margin-bottom: 24px;
        }

        .feature-mark svg {
            width: 26px;
            height: 26px;
            display: block;
        }

        .service-mark {
            width: 64px;
            height: 64px;
            border-radius: 20px;
            background: #fff8c7;
            border: 1px solid rgba(31, 31, 31, 0.08);
            color: #1f1f1f;
            display: flex;
            align-items: center;
            justify-content: center;
            box-shadow: inset 0 0 0 1px rgba(254, 229, 0, 0.45);
            transition: transform 0.3s ease;
            flex-shrink: 0;
        }

        .group:hover .service-mark {
            transform: scale(1.05);
        }

        .service-mark svg {
            width: 31px;
            height: 31px;
            display: block;
        }

        .message-input-wrap {
            flex: 1;
            min-width: 0;
            position: relative;
            display: flex;
            align-items: center;
        }

        .message-input {
            width: 100%;
            border-radius: 18px;
            border: 1px solid #dedede;
            background: #ffffff;
            padding: 12px 46px 12px 14px;
            font-size: 14px;
            resize: none;
            height: 44px;
            color: #1f1f1f;
            font-family: inherit;
        }

        .message-input-icon-btn {
            position: absolute;
            right: 8px;
            top: 50%;
            transform: translateY(-50%);
            width: 30px;
            height: 30px;
            border-radius: 12px;
            color: #6f6f6f;
            display: inline-flex;
            align-items: center;
            justify-content: center;
        }

        .message-input-icon-btn svg {
            width: 18px;
            height: 18px;
            display: block;
        }

        .send-controls {
            display: flex;
            flex-direction: column;
            gap: 8px;
            width: 74px;
            flex-shrink: 0;
        }

        .send-button {
            background: #fee500;
            border: none;
            color: #111827;
            font-weight: 700;
            height: 44px;
            border-radius: 16px;
            font-size: 14px;
            width: 100%;
            cursor: pointer;
        }

        .opacity-slider {
            width: 100%;
            height: 4px;
            -webkit-appearance: none;
            background: #e5e7eb;
            border-radius: 999px;
            outline: none;
        }

        .opacity-slider::-webkit-slider-thumb {
            -webkit-appearance: none;
            width: 12px;
            height: 12px;
            border-radius: 50%;
            background: #fee500;
            cursor: pointer;
            margin-top: 0px;
        }

        /* Modal Styles */
        .modal-backdrop {
            position: fixed;
            inset: 0;
            background: rgba(0, 0, 0, 0.5);
            display: flex;
            align-items: center;
            justify-content: center;
            z-index: 100;
            opacity: 0;
            pointer-events: none;
            transition: opacity 0.3s ease;
            backdrop-filter: blur(4px);
        }

        .modal-backdrop.active {
            opacity: 1;
            pointer-events: auto;
        }

        .modal-content {
            background: white;
            width: 90%;
            max-width: 600px;
            border-radius: 24px;
            padding: 2.5rem;
            max-height: 80vh;
            overflow-y: auto;
            transform: translateY(20px);
            transition: transform 0.3s ease;
            box-shadow: 0 20px 60px rgba(0, 0, 0, 0.2);
        }

        .modal-backdrop.active .modal-content {
            transform: translateY(0);
        }

        /* FAQ Accordion */
        .faq-item {
            border-bottom: 1px solid var(--color-border);
        }

        .faq-item:last-child {
            border-bottom: none;
        }

        .faq-button {
            width: 100%;
            text-align: left;
            padding: 1.5rem 0;
            font-weight: 600;
            display: flex;
            justify-content: space-between;
            align-items: center;
        }

        .faq-content {
            max-height: 0;
            overflow: hidden;
            transition: max-height 0.3s ease-out;
            color: #6f6f6f;
            line-height: 1.6;
        }

        .faq-item.active .faq-content {
            max-height: 200px;
            padding-bottom: 1.5rem;
        }

        .faq-icon {
            transition: transform 0.3s ease;
        }

        .faq-item.active .faq-icon {
            transform: rotate(180deg);
        }

        html,
        body,
        .mockup-container,
        .window-frame,
        .list-item,
        .bubble,
        .chat-messages,
        .faq-item {
            -webkit-user-drag: none;

            -webkit-user-select: none;
            -ms-user-select: none;
            user-select: none;
        }

        input,
        textarea,
        select,
        button,
        .message-input,
        .message-input * {
            -webkit-user-select: text !important;
            -ms-user-select: text !important;
            user-select: text !important;
            -webkit-user-drag: auto !important;

        }