:root {
            --bg-color: #f8f9fa;
            --text-color: #212529;
            --editor-bg: #ffffff;
            --border-color: #dee2e6;
            --accent-color: #6c757d;
            --hover-color: #495057;
            --info-bg: #e9ecef;
            --button-bg: #f8f9fa;
            --success-color: #28a745;
            --error-color: #dc3545;
            --logo-color: #0d6efd;
            --toolbar-gap: 5px;
            --header-height: 50px;
        }

        [data-theme="dark"] {
            --bg-color: #212529;
            --text-color: #f8f9fa;
            --editor-bg: #343a40;
            --border-color: #495057;
            --accent-color: #adb5bd;
            --hover-color: #ced4da;
            --info-bg: #343a40;
            --button-bg: #343a40;
            --logo-color: #4d94ff;
        }

        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            transition: background-color 0.3s, color 0.3s;
            -webkit-tap-highlight-color: transparent;
        }

        body {
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
            margin: 0;
            padding: 0;
            background-color: var(--bg-color);
            color: var(--text-color);
            height: 100vh;
            display: flex;
            flex-direction: column;
            overflow-x: hidden;
        }

        .logo {
            display: flex;
            align-items: center;
            font-weight: bold;
            font-size: 18px;
            color: var(--logo-color);
            white-space: nowrap;
        }

        .logo-icon {
            margin-right: 5px;
            width: 25px;
            height: 25px;
            border-radius: 50%;
            background-color: var(--logo-color);
            display: flex;
            align-items: center;
            justify-content: center;
            color: white;
            flex-shrink: 0;
        }

        .header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 8px 12px;
            background-color: var(--info-bg);
            border-bottom: 1px solid var(--border-color);
            height: var(--header-height);
            position: sticky;
            top: 0;
            z-index: 100;
        }

        .header-right {
            display: flex;
            align-items: center;
        }

        .header-left {
            display: flex;
            align-items: center;
            gap: 8px;
            overflow-x: auto;
            scrollbar-width: none;
            /* Firefox */
            -ms-overflow-style: none;
            /* IE and Edge */
        }

        .header-left::-webkit-scrollbar {
            display: none;
            /* Chrome, Safari, Opera */
        }

        .toolbar {
            display: flex;
            padding: 8px 12px;
            background-color: var(--info-bg);
            border-bottom: 1px solid var(--border-color);
            flex-wrap: wrap;
            gap: var(--toolbar-gap);
            position: sticky;
            top: var(--header-height);
            z-index: 99;
            overflow-x: auto;
            scrollbar-width: none;
            -ms-overflow-style: none;
        }

        .toolbar::-webkit-scrollbar {
            display: none;
        }

        .toolbar-btn {
            background: var(--button-bg);
            border: 1px solid var(--border-color);
            color: var(--accent-color);
            cursor: pointer;
            font-size: 14px;
            padding: 6px 10px;
            border-radius: 4px;
            display: flex;
            align-items: center;
            justify-content: center;
            min-width: 36px;
            touch-action: manipulation;
        }

        .toolbar-btn:hover {
            background-color: var(--hover-color);
            color: var(--text-color);
        }

        .toolbar-btn:active {
            transform: scale(0.95);
        }

        .toolbar-select {
            background: var(--button-bg);
            border: 1px solid var(--border-color);
            color: var(--text-color);
            padding: 6px 8px;
            border-radius: 4px;
            cursor: pointer;
            max-width: 120px;
            appearance: menulist;
        }

        .theme-toggle,
        .action-btn {
            background: none;
            border: 1px solid transparent;
            color: var(--accent-color);
            cursor: pointer;
            font-size: 16px;
            padding: 5px 8px;
            border-radius: 4px;
            margin-left: 10px;
            display: flex;
            align-items: center;
            white-space: nowrap;
        }

        .theme-toggle:hover,
        .action-btn:hover {
            color: var(--hover-color);
            border-color: var(--border-color);
        }

        .action-btn i {
            margin-right: 4px;
        }

        .word-counter {
            color: var(--accent-color);
            font-size: 12px;
            display: flex;
            align-items: center;
            white-space: nowrap;
        }

        .container {
            flex: 1;
            padding: 10px;
            max-width: 900px;
            width: 100%;
            margin: 0 auto;
            display: flex;
            flex-direction: column;
            overflow-y: auto;
        }

        #editor {
            width: 100%;
            height: 100%;
            flex-grow: 1;
            padding: 16px;
            font-size: 16px;
            line-height: 1.6;
            border: 1px solid var(--border-color);
            border-radius: 5px;
            background-color: var(--editor-bg);
            color: var(--text-color);
            outline: none;
            overflow-y: auto;
            margin-bottom: 10px;
            -webkit-overflow-scrolling: touch;
        }

        #editor:focus {
            border-color: var(--accent-color);
            box-shadow: 0 0 0 2px rgba(108, 117, 125, 0.2);
        }

        .alert {
            position: fixed;
            top: 20px;
            left: 50%;
            transform: translateX(-50%) translateY(-100px);
            padding: 10px 20px;
            border-radius: 5px;
            color: white;
            font-weight: bold;
            transition: transform 0.3s ease-in-out;
            z-index: 1000;
            text-align: center;
            max-width: 90%;
            word-wrap: break-word;
            box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
        }

        .alert.show {
            transform: translateX(-50%) translateY(0);
        }

        .alert-success {
            background-color: var(--success-color);
        }

        .alert-error {
            background-color: var(--error-color);
        }

        /* ─── Tab Bar ────────────────────────────────────────── */
        .tab-bar {
            display: flex;
            align-items: center;
            gap: 2px;
            padding: 6px 12px;
            background: var(--info-bg);
            border-bottom: 1px solid var(--border-color);
            overflow-x: auto;
            scrollbar-width: none;
            -ms-overflow-style: none;
            position: sticky;
            top: calc(var(--header-height) + 41px);
            z-index: 98;
        }

        .tab-bar::-webkit-scrollbar {
            display: none;
        }

        .tab {
            display: flex;
            align-items: center;
            gap: 4px;
            padding: 6px 12px;
            background: var(--button-bg);
            border: 1px solid var(--border-color);
            border-bottom: 2px solid transparent;
            border-radius: 6px 6px 0 0;
            cursor: pointer;
            font-size: 13px;
            color: var(--accent-color);
            white-space: nowrap;
            max-width: 180px;
            position: relative;
            transition: all 0.2s ease;
            animation: tabSlideIn 0.25s ease-out;
        }

        @keyframes tabSlideIn {
            from {
                opacity: 0;
                transform: translateY(-8px) scale(0.95);
            }
            to {
                opacity: 1;
                transform: translateY(0) scale(1);
            }
        }

        .tab:hover {
            background: var(--editor-bg);
            color: var(--text-color);
        }

        .tab.active {
            background: var(--editor-bg);
            color: var(--text-color);
            border-bottom-color: var(--logo-color);
            font-weight: 600;
            box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
        }

        .tab-title {
            overflow: hidden;
            text-overflow: ellipsis;
            max-width: 140px;
            user-select: none;
        }

        .tab-close {
            display: flex;
            align-items: center;
            justify-content: center;
            background: none;
            border: none;
            color: var(--accent-color);
            cursor: pointer;
            font-size: 10px;
            width: 18px;
            height: 18px;
            border-radius: 50%;
            padding: 0;
            opacity: 0;
            transition: all 0.15s ease;
            flex-shrink: 0;
        }

        .tab:hover .tab-close,
        .tab.active .tab-close {
            opacity: 0.6;
        }

        .tab-close:hover {
            opacity: 1 !important;
            background: var(--error-color);
            color: white;
        }

        .tab-rename-input {
            background: var(--editor-bg);
            border: 1px solid var(--logo-color);
            color: var(--text-color);
            font-size: 13px;
            padding: 1px 4px;
            border-radius: 3px;
            width: 120px;
            outline: none;
            font-family: inherit;
        }

        .tab-add {
            display: flex;
            align-items: center;
            justify-content: center;
            background: none;
            border: 1px dashed var(--border-color);
            color: var(--accent-color);
            cursor: pointer;
            font-size: 12px;
            width: 30px;
            height: 30px;
            border-radius: 6px 6px 0 0;
            padding: 0;
            flex-shrink: 0;
            transition: all 0.2s ease;
        }

        .tab-add:hover {
            background: var(--editor-bg);
            border-color: var(--logo-color);
            color: var(--logo-color);
            transform: scale(1.05);
        }

        .tab-add:active {
            transform: scale(0.95);
        }

        /* Mobile optimizations */
        @media (max-width: 768px) {
            .container {
                padding: 8px;
            }

            #editor {
                padding: 12px;
                font-size: 16px;
                border-radius: 4px;
            }

            .toolbar {
                padding: 6px 8px;
                overflow-x: auto;
                justify-content: flex-start;
                flex-wrap: nowrap;
            }

            .logo {
                font-size: 16px;
            }

            .logo-icon {
                width: 20px;
                height: 20px;
            }

            .action-btn span {
                display: none;
            }

            .action-btn i {
                margin-right: 0;
            }

            .toolbar-btn {
                padding: 8px;
                min-width: 36px;
                height: 36px;
            }

            .toolbar-select {
                max-width: 90px;
                font-size: 12px;
            }

            .theme-toggle,
            .action-btn {
                margin-left: 6px;
                padding: 6px;
            }

            .header-left {
                gap: 4px;
            }

            .word-counter {
                font-size: 10px;
                max-width: 120px;
                white-space: nowrap;
                overflow: hidden;
                text-overflow: ellipsis;
            }

            .tab-bar {
                padding: 4px 8px;
                gap: 2px;
            }

            .tab {
                padding: 5px 10px;
                font-size: 12px;
                max-width: 140px;
            }

            .tab-title {
                max-width: 100px;
            }

            .tab-add {
                width: 28px;
                height: 28px;
            }
        }

        /* Small mobile phones */
        @media (max-width: 480px) {
            .header {
                padding: 6px 8px;
            }

            .toolbar {
                gap: 4px;
            }

            #editor {
                padding: 10px;
                font-size: 15px;
            }

            .toolbar-btn {
                min-width: 32px;
                height: 32px;
                font-size: 12px;
            }

            .toolbar-select {
                max-width: 80px;
                padding: 4px 6px;
            }

            .tab {
                padding: 4px 8px;
                font-size: 11px;
                max-width: 120px;
            }

            .tab-title {
                max-width: 80px;
            }

            .tab-rename-input {
                width: 80px;
                font-size: 11px;
            }
        }

        /* Fix for iOS Safari's 100vh bug */
        @supports (-webkit-touch-callout: none) {

            body,
            .container {
                height: -webkit-fill-available;
            }
        }

        /* Support for notched devices */
        @media screen and (orientation: portrait) {
            .header {
                padding-top: max(8px, env(safe-area-inset-top));
                padding-left: max(12px, env(safe-area-inset-left));
                padding-right: max(12px, env(safe-area-inset-right));
            }

            .container {
                padding-bottom: max(10px, env(safe-area-inset-bottom));
                padding-left: max(10px, env(safe-area-inset-left));
                padding-right: max(10px, env(safe-area-inset-right));
            }
        }