/* --- CSS Variables --- */
        :root {
            --primary-color: #0056b3;
            --bg-color: #f4f7f9;
            --panel-bg: #ffffff;
            --input-bg: #ffffff;
            --tool-bg: #eef2f5;
            --text-color: #333333;
            --text-muted: #666666;
            --border-color: #dddddd;
            --error-color: #dc3545;
            --success-color: #28a745;
            --warning-bg: rgba(255, 193, 7, 0.15);
            --warning-border: rgba(255, 193, 7, 0.5);
            --warning-text: #856404;
            --hover-bg: #f0f0f0;
            --shadow: 0 2px 8px rgba(0,0,0,0.08);
            --header-height: 60px;
        }

        [data-theme="dark"] {
            --primary-color: #4da3ff;
            --bg-color: #121212;
            --panel-bg: #1e1e1e;
            --input-bg: #2d2d2d;
            --tool-bg: #252525;
            --text-color: #e0e0e0;
            --text-muted: #a0a0a0;
            --border-color: #444444;
            --error-color: #ff6b6b;
            --success-color: #4cd964;
            --warning-bg: rgba(255, 193, 7, 0.1);
            --warning-border: rgba(255, 193, 7, 0.3);
            --warning-text: #ffda6a;
            --hover-bg: #333333;
            --shadow: 0 2px 8px rgba(0,0,0,0.3);
        }

        body {
            font-family: "Helvetica Neue", Arial, sans-serif;
            line-height: 1.6;
            color: var(--text-color);
            background-color: var(--bg-color);
            margin: 0; padding: 0;
            transition: background-color 0.3s, color 0.3s;
        }

        a { text-decoration: none; color: var(--primary-color); }
        a:hover { text-decoration: underline; }

        /* Header */
        header {
            background-color: var(--panel-bg);
            border-bottom: 1px solid var(--border-color);
            height: var(--header-height);
            position: sticky; top: 0; z-index: 100;
            box-shadow: 0 1px 4px rgba(0,0,0,0.05);
        }
        .nav-container {
            max-width: 1000px; margin: 0 auto; padding: 0 20px;
            height: 100%; display: flex; justify-content: space-between; align-items: center;
            position: relative;
        }
        .logo { font-size: 20px; margin: 0; font-weight: bold; color: var(--text-color); display: flex; align-items: center; gap: 10px; }
        
        /* Desktop Navigation */
        .nav-links { display: flex; align-items: center; gap: 20px; margin-left: auto; margin-right: 20px; }
        .nav-links a { color: var(--text-muted); font-size: 14px; font-weight: 500; transition: color 0.2s; }
        .nav-links a:hover { color: var(--primary-color); text-decoration: none; }
        
        /* Active State Style */
        .nav-links a.current {
            color: var(--primary-color);
            font-weight: bold;
            position: relative;
        }
        .nav-links a.current::after {
            content: '';
            position: absolute;
            left: 0;
            bottom: -5px;
            width: 100%;
            height: 2px;
            background-color: var(--primary-color);
            border-radius: 2px;
        }
        
        /* Right Side Actions (Theme + Hamburger) */
        .header-actions { display: flex; align-items: center; gap: 10px; }

        #theme-toggle { background: none; border: 1px solid var(--border-color); border-radius: 20px; width: 40px; height: 32px; padding: 0; cursor: pointer; color: var(--text-color); display: flex; align-items: center; justify-content: center; transition: all 0.2s; }
        #theme-toggle:hover { background-color: var(--hover-bg); }

        /* Hamburger Menu (Hidden by default) */
        .hamburger {
            display: none;
            background: transparent;
            border: none;
            cursor: pointer;
            padding: 0;
            z-index: 101;
            color: var(--text-color);
        }

        /* Main Container */
        .container {
            max-width: 800px; margin: 40px auto; background: var(--panel-bg);
            padding: 40px; border-radius: 8px; box-shadow: var(--shadow);
            border: 1px solid var(--border-color);
        }
        
        .section-title { 
            margin: 0 0 15px 0; 
            font-size: 20px; 
            border-left: 5px solid var(--primary-color); 
            padding-left: 10px; 
            color: var(--text-color);
            font-weight: bold;
            line-height: 1.2;
            scroll-margin-top: 80px; 
        }

        #chart {
            margin-top: 20px;
            padding-top: 10px;
        }

        /* --- Tool Controls (Tabs & Clear Button) --- */
        .tool-controls {
            display: flex;
            justify-content: space-between;
            align-items: stretch;
            gap: 12px;
            margin-bottom: 6px;
        }

        .quick-mode {
            display: flex;
            flex-grow: 1;
            padding: 4px;
            background: var(--tool-bg);
            border: 1px solid var(--border-color);
            border-radius: 6px;
            gap: 4px;
        }
        .quick-mode-btn {
            flex: 1;
            min-height: 40px;
            border: 0;
            border-radius: 4px;
            background: transparent;
            color: var(--text-muted);
            cursor: pointer;
            font-size: 13px;
            font-weight: bold;
            transition: all 0.2s;
        }
        .quick-mode-btn:hover { color: var(--text-color); background: var(--hover-bg); }
        .quick-mode-btn.active {
            background: var(--panel-bg);
            color: var(--primary-color);
            box-shadow: 0 1px 4px rgba(0,0,0,0.12);
        }

        .clear-btn { 
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 6px;
            background: transparent;
            border: 1px solid var(--border-color); 
            color: var(--error-color); 
            padding: 0 16px;
            font-size: 13px; 
            font-weight: bold;
            border-radius: 6px; 
            cursor: pointer; 
            transition: all 0.2s; 
            white-space: nowrap;
            box-shadow: 0 1px 2px rgba(0,0,0,0.05);
        }
        .clear-btn:hover { 
            background: rgba(220, 53, 69, 0.1); 
            border-color: var(--error-color); 
        }

        .quick-mode-help {
            margin: 0 0 20px 4px;
            color: var(--text-muted);
            font-size: 12px;
        }

        /* --- Overflow Warning Message --- */
        .overflow-msg {
            background-color: var(--warning-bg);
            border: 1px solid var(--warning-border);
            color: var(--warning-text);
            padding: 10px 15px;
            border-radius: 6px;
            margin-bottom: 20px;
            font-size: 13px;
            font-weight: bold;
            display: none; /* Hidden by default */
            align-items: center;
            gap: 8px;
            animation: fadeIn 0.3s ease;
        }
        @keyframes fadeIn { from { opacity: 0; transform: translateY(-5px); } to { opacity: 1; transform: translateY(0); } }

        .noscript-message {
            padding: 12px 15px;
            border: 1px solid var(--warning-border);
            border-radius: 6px;
            background: var(--warning-bg);
            color: var(--warning-text);
            font-weight: bold;
        }

        /* Usage List Styling */
        .usage-list {
            padding-left: 20px;
            color: var(--text-color);
            margin-bottom: 30px;
        }
        .usage-list li {
            margin-bottom: 8px;
            line-height: 1.6;
        }

        /* Tool Container */
        .tool-container { background-color: var(--tool-bg); padding: 25px; border-radius: 6px; border: 1px solid var(--border-color); margin-bottom: 14px; }
        .input-group { margin-bottom: 20px; }
        .input-group:last-child { margin-bottom: 0; }
        .input-group label { display: block; font-weight: bold; margin-bottom: 8px; font-size: 14px; color: var(--text-muted); }
        .input-wrapper { display: flex; gap: 8px; align-items: flex-start; position: relative; }
        .input-box-container { flex-grow: 1; display: flex; flex-direction: column; position: relative; }

        input[type="text"] {
            width: 100%; padding: 12px; 
            font-size: 16px;
            border: 1px solid var(--border-color); border-radius: 4px;
            background-color: var(--input-bg); color: var(--text-color);
            transition: border-color 0.2s; box-sizing: border-box; height: 48px;
            font-family: "Menlo", "Consolas", "Monaco", "Courier New", monospace;
        }
        input[type="text"]:focus { border-color: var(--primary-color); }

        :where(button, a, input, select, summary):focus-visible {
            outline: 3px solid var(--primary-color);
            outline-offset: 3px;
        }
        
        input[type="text"].is-invalid { border-color: var(--error-color); background-color: rgba(220, 53, 69, 0.05); }
        .error-msg { color: var(--error-color); font-size: 12px; margin-top: 4px; font-weight: bold; display: none; }

        .copy-btn {
            position: relative; /* Base for toast positioning */
            display: flex; align-items: center; justify-content: center; height: 48px; padding: 0 15px;
            background-color: var(--panel-bg); border: 1px solid var(--border-color); border-radius: 4px;
            cursor: pointer; font-size: 14px; color: var(--text-color); transition: all 0.2s; min-width: 70px; white-space: nowrap;
        }
        .copy-btn:hover:not(:disabled) { background-color: var(--hover-bg); }
        
        /* 修复悬停导致的复制成功样式失效问题 */
        .copy-btn.copied, .copy-btn.copied:hover { 
            background-color: var(--success-color) !important; 
            color: #fff !important; 
            border-color: var(--success-color) !important; 
        }
        
        /* Disabled state for copy buttons */
        .copy-btn:disabled {
            opacity: 0.5;
            cursor: not-allowed;
            background-color: var(--panel-bg) !important;
            color: var(--text-muted) !important;
            border-color: var(--border-color) !important;
        }

        /* Toast for copy format info */
        .copy-toast {
            position: absolute;
            bottom: calc(100% + 8px);
            left: 50%;
            transform: translateX(-50%);
            background: rgba(0,0,0,0.8);
            color: #fff;
            padding: 6px 10px;
            border-radius: 4px;
            font-size: 11px;
            white-space: nowrap;
            pointer-events: none;
            opacity: 0;
            transition: opacity 0.2s;
            z-index: 100;
            box-shadow: 0 2px 6px rgba(0,0,0,0.2);
        }
        .copy-toast::after {
            content: '';
            position: absolute;
            top: 100%;
            left: 50%;
            margin-left: -4px;
            border-width: 4px;
            border-style: solid;
            border-color: rgba(0,0,0,0.8) transparent transparent transparent;
        }
        [data-theme="dark"] .copy-toast {
            background: var(--primary-color);
            color: #fff;
        }
        [data-theme="dark"] .copy-toast::after {
            border-color: var(--primary-color) transparent transparent transparent;
        }

        /* Color Preview */
        .input-with-preview input { padding-right: 50px; }
        .color-box {
            position: absolute; right: 10px; top: 8px; width: 32px; height: 32px;
            border-radius: 4px; border: 1px solid rgba(0,0,0,0.1); display: none;
            background-image: linear-gradient(45deg, #ccc 25%, transparent 25%), linear-gradient(-45deg, #ccc 25%, transparent 25%), linear-gradient(45deg, transparent 75%, #ccc 75%), linear-gradient(-45deg, transparent 75%, #ccc 75%);
            background-size: 10px 10px; background-position: 0 0, 0 5px, 5px -5px, -5px 0px;
        }
        .color-inner { width: 100%; height: 100%; border-radius: 3px; }

        .advanced-settings {
            margin-top: 14px;
            border: 1px solid var(--border-color);
            border-radius: 8px;
            background: var(--panel-bg);
            overflow: hidden;
            scroll-margin-top: 80px;
        }
        .advanced-settings > summary {
            padding: 16px 18px;
            display: flex;
            justify-content: space-between;
            gap: 15px;
            align-items: center;
            background: var(--panel-bg);
            cursor: pointer;
            list-style: none;
        }
        .advanced-settings > summary::-webkit-details-marker { display: none; }
        .advanced-settings > summary::after {
            content: "開く ＋";
            color: var(--primary-color);
            font-size: 12px;
            white-space: nowrap;
        }
        .advanced-settings[open] > summary::after { content: "閉じる −"; }
        .advanced-summary-title { display: block; font-size: 15px; font-weight: bold; color: var(--text-color); }
        .advanced-summary-desc { display: block; margin-top: 2px; color: var(--text-muted); font-size: 12px; font-weight: normal; }
        .advanced-body { padding: 0 20px 22px; border-top: 1px solid var(--border-color); }

        .settings-panel {
            padding: 22px 0; border-bottom: 1px solid var(--border-color);
        }
        .settings-panel:last-of-type { border-bottom: 0; }
        .settings-header { display: flex; align-items: center; gap: 10px; margin-bottom: 20px; padding-bottom: 10px; border-bottom: 1px solid var(--border-color); }
        .settings-header h3 { margin: 0; font-size: 16px; color: var(--text-color); }
        .settings-grid { display: grid; grid-template-columns: 1fr; gap: 20px; }
        .setting-item { display: flex; flex-direction: column; gap: 8px; }
        .setting-row { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 10px; }
        .setting-label { font-weight: bold; color: var(--text-color); font-size: 14px; min-width: 100px; }
        .setting-desc { font-size: 12px; color: var(--text-muted); margin: 0; line-height: 1.4; background-color: var(--bg-color); padding: 8px 12px; border-radius: 4px; }
        select { padding: 8px 12px; min-width: 180px; border-radius: 4px; border: 1px solid var(--border-color); background-color: var(--input-bg); color: var(--text-color); font-size: 14px; cursor: pointer; }
        select:disabled { opacity: 0.55; cursor: not-allowed; }
        .setting-note { margin: 18px 0 0; padding: 10px 12px; border-left: 3px solid var(--primary-color); background: var(--bg-color); color: var(--text-muted); font-size: 12px; line-height: 1.6; }

        .byte-order-panel {
            padding: 22px 0 0;
        }
        .byte-order-panel h3 { margin: 0 0 6px; font-size: 16px; }
        .byte-order-panel > p { margin: 0 0 16px; color: var(--text-muted); font-size: 12px; }
        .byte-row { display: grid; grid-template-columns: 110px 1fr auto; gap: 10px; align-items: center; margin-top: 10px; }
        .byte-label { color: var(--text-muted); font-size: 13px; font-weight: bold; }
        .byte-value {
            min-width: 0; padding: 10px 12px; border: 1px solid var(--border-color); border-radius: 4px;
            background: var(--input-bg); color: var(--text-color); font: 14px/1.4 "Menlo", "Consolas", monospace;
            overflow-x: auto; white-space: nowrap;
        }
        .byte-copy { height: 40px; min-width: 60px; }

        /* --- Chart / Reference Table Styles --- */
        .chart-container {
            position: relative;
            overflow: hidden;
            border: 1px solid var(--border-color);
            border-radius: 6px;
            margin-bottom: 10px;
        }

        .reference-table-wrapper { width: 100%; }
        table.ref-table { width: 100%; border-collapse: collapse; font-size: 14px; text-align: center; }
        table.ref-table th { 
            background-color: var(--tool-bg); color: var(--text-muted); padding: 12px; 
            border-bottom: 2px solid var(--border-color); position: sticky; top: 0;
        }
        table.ref-table td { 
            padding: 8px; border-bottom: 1px solid var(--border-color); 
            font-family: "Consolas", "Monaco", "Courier New", monospace; color: var(--text-color); 
        }
        table.ref-table tr:nth-child(even) { background-color: var(--bg-color); }
        [data-theme="dark"] table.ref-table tr:nth-child(even) { background-color: rgba(255,255,255,0.03); }
        
        /* FAQ Styles */
        .faq-section { margin-top: 50px; }
        details.faq-item { border: 1px solid var(--border-color); border-radius: 6px; background: var(--input-bg); margin-bottom: 10px; overflow: hidden; }
        details.faq-item summary { padding: 15px; cursor: pointer; font-weight: bold; color: var(--text-color); outline: none; transition: background-color 0.2s; list-style: none; display: flex; align-items: center; justify-content: space-between; }
        details.faq-item summary:focus-visible { outline: 3px solid var(--primary-color); outline-offset: -3px; }
        details.faq-item summary::-webkit-details-marker { display: none; }
        details.faq-item summary::after { content: '+'; font-size: 18px; color: var(--primary-color); font-weight: normal; }
        details.faq-item[open] summary::after { content: '−'; }
        details.faq-item summary:hover { background-color: var(--hover-bg); }
        .faq-answer { padding: 15px; font-size: 14px; color: var(--text-muted); border-top: 1px solid var(--border-color); background-color: var(--bg-color); line-height: 1.6; }

        .usage-steps {
            margin: 0 0 30px;
            padding-left: 1.5em;
        }
        .usage-steps li { margin-bottom: 12px; }
        .usage-steps li:last-child { margin-bottom: 0; }

        /* Back to Top */
        #back-to-top {
            position: fixed; bottom: 30px; right: 30px; width: 50px; height: 50px;
            background-color: var(--primary-color); color: #fff; border: none; border-radius: 50%;
            font-size: 24px; cursor: pointer; box-shadow: 0 4px 10px rgba(0,0,0,0.2);
            opacity: 0; visibility: hidden; transform: translateY(20px); transition: all 0.3s ease;
            z-index: 1000; display: flex; align-items: center; justify-content: center;
        }
        #back-to-top.show { opacity: 1; visibility: visible; transform: translateY(0); }
        #back-to-top:hover { transform: translateY(-5px); filter: brightness(1.1); }

        /* SNS Share Styles */
        .share-section { text-align: center; margin: 60px 0 20px; padding: 0 20px; }
        .share-section h3 { font-size: 16px; margin-bottom: 20px; color: var(--text-muted); font-weight: bold; }
        .share-buttons { display: flex; justify-content: center; gap: 12px; flex-wrap: wrap; }
        .share-btn {
            display: inline-flex; align-items: center; justify-content: center;
            padding: 10px 0; border-radius: 4px; color: #fff; font-weight: bold;
            text-decoration: none; transition: opacity 0.2s, transform 0.2s; 
            font-size: 14px; width: 100px;
        }
        .share-btn:hover { opacity: 0.9; text-decoration: none; color: #fff; transform: translateY(-2px); }
        .btn-x { background-color: #000; }
        .btn-fb { background-color: #1877f2; }
        .btn-line { background-color: #06c755; }
        .btn-hatena { background-color: #00a4de; }

        footer { background-color: var(--tool-bg); border-top: 1px solid var(--border-color); padding: 40px 0 20px; margin-top: 60px; font-size: 14px; }
        .footer-content { max-width: 1000px; margin: 0 auto; padding: 0 20px; display: flex; justify-content: space-between; flex-wrap: wrap; gap: 20px; }
        .footer-links { display: flex; gap: 20px; font-size: 12px;  } .footer-links a { color: var(--text-muted); }
        .copyright { text-align: center; margin-top: 30px; color: var(--text-muted); font-size: 12px; }

        @media (min-width: 600px) {
            .setting-item { display: grid; grid-template-columns: 240px 1fr; align-items: center; gap: 20px; }
            .setting-row { flex-direction: column; align-items: flex-start; width: 100%; }
            select { width: 100%; }
            .setting-desc { margin-top: 0; }
        }

        /* ✅ Mobile Navigation Styles */
        @media (max-width: 600px) {
            .container { padding: 20px; margin: 20px auto; }
            .logo { font-size: 18px; }
            
            /* Hide NavLinks in Header Flow */
            .nav-links {
                display: none; 
                position: absolute;
                top: 60px; /* Below header */
                left: 0; right: 0;
                background-color: var(--panel-bg);
                flex-direction: column;
                align-items: center;
                padding: 20px;
                border-bottom: 1px solid var(--border-color);
                box-shadow: 0 10px 20px rgba(0,0,0,0.1);
                gap: 15px;
                margin: 0; /* Reset margins */
            }
            .nav-links.active { display: flex; animation: slideDown 0.3s ease; }
            .nav-links a { display: block; width: 100%; text-align: center; padding: 10px 0; font-size: 16px; border-bottom: 1px solid var(--tool-bg); }
            .nav-links a:last-of-type { border-bottom: none; }

            /* Mobile Active Link Adjustments */
            .nav-links a.current::after {
                display: none; /* Hide underline on mobile */
            }
            .nav-links a.current {
                background-color: var(--tool-bg); /* Use background instead */
                border-radius: 4px;
            }
            
            /* Hamburger Visible */
            .hamburger { display: flex; align-items: center; justify-content: center; }
            
            .input-wrapper { flex-direction: row; } .copy-btn { padding: 0 10px; min-width: 60px; font-size: 12px; }
            .footer-content { flex-direction: column; text-align: center; } .footer-links { justify-content: center; }
            
            /* 新版头部控制栏响应式 */
            .tool-controls { gap: 8px; }
            .quick-mode-btn { font-size: 12px; padding: 0; }
            .clear-text { display: none; }
            .clear-btn { padding: 0; width: 48px; flex-shrink: 0; }
            
            .advanced-settings > summary { align-items: flex-start; }
            .advanced-body { padding: 0 16px 18px; }
            .byte-row { grid-template-columns: 1fr auto; }
            .byte-label { grid-column: 1 / -1; }
            #back-to-top { bottom: 20px; right: 20px; width: 44px; height: 44px; font-size: 20px; }
            .share-btn { width: 45%; }
        }

        @keyframes slideDown {
            from { opacity: 0; transform: translateY(-10px); }
            to { opacity: 1; transform: translateY(0); }
        }

        @media (prefers-reduced-motion: reduce) {
            *, *::before, *::after {
                scroll-behavior: auto !important;
                animation-duration: 0.01ms !important;
                animation-iteration-count: 1 !important;
                transition-duration: 0.01ms !important;
            }
        }