/* ── Theme variables ────────────────────────────────────────────── */
        :root {
            /* Night (default) */
            --bg-gradient:       linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
            --accent:            #00d4ff;
            --accent-dark:       #0099cc;
            --body-text:         #e0e0e0;
            --label-text:        #8892b0;
            --panel-bg:          rgba(255,255,255,0.05);
            --panel-border:      rgba(255,255,255,0.1);
            --panel-shadow:      0 8px 32px rgba(0,0,0,0.3);
            --input-bg:          #1e2a3a;
            --input-bg-hover:    #243347;
            --input-border:      #3a5068;
            --input-text:        #e0e0e0;
            --select-option-bg:  #1a2535;
            --btn-secondary-bg:  rgba(255,255,255,0.1);
            --btn-secondary-fg:  #e0e0e0;
            --btn-secondary-bdr: rgba(255,255,255,0.2);
            --terminal-bg:       rgba(0,0,0,0.3);
            --terminal-border:   rgba(255,255,255,0.1);
            --statusbar-bg:      rgba(0,0,0,0.8);
            --statusbar-border:  rgba(255,255,255,0.1);
            --timestamp-color:   #5a6a7a;
            --data-hex-color:    #a8a8a8;
            --data-ascii-color:  #90ee90;
            --scrollbar-track:   rgba(0,0,0,0.2);
            --scrollbar-thumb:   rgba(255,255,255,0.2);
            --scrollbar-hover:   rgba(255,255,255,0.35);
            --tab-inactive:      #8892b0;
        }

        body.day {
            --bg-gradient:       linear-gradient(135deg, #dde8f5 0%, #c8dcf0 100%);
            --accent:            #0077bb;
            --accent-dark:       #005a99;
            --body-text:         #1a2a3a;
            --label-text:        #4a5a72;
            --panel-bg:          rgba(255,255,255,0.75);
            --panel-border:      rgba(0,80,160,0.15);
            --panel-shadow:      0 8px 32px rgba(0,60,120,0.12);
            --input-bg:          #ffffff;
            --input-bg-hover:    #f0f6ff;
            --input-border:      #96b8d8;
            --input-text:        #1a2a3a;
            --select-option-bg:  #ffffff;
            --btn-secondary-bg:  rgba(0,80,160,0.08);
            --btn-secondary-fg:  #1a2a3a;
            --btn-secondary-bdr: rgba(0,80,160,0.25);
            --terminal-bg:       #f4f8ff;
            --terminal-border:   rgba(0,80,160,0.15);
            --statusbar-bg:      rgba(220,235,250,0.95);
            --statusbar-border:  rgba(0,80,160,0.15);
            --timestamp-color:   #7a8fa8;
            --data-hex-color:    #4a6888;
            --data-ascii-color:  #1a7a3a;
            --scrollbar-track:   rgba(0,0,0,0.05);
            --scrollbar-thumb:   rgba(0,80,160,0.25);
            --scrollbar-hover:   rgba(0,80,160,0.45);
            --tab-inactive:      #4a6888;
        }

        /* ── Reset ──────────────────────────────────────────────────────── */
        * { margin: 0; padding: 0; box-sizing: border-box; }

        body {
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto,
                         'Helvetica Neue', Arial, sans-serif;
            background: var(--bg-gradient);
            min-height: 100vh;
            padding: 20px;
            padding-bottom: 60px;
            color: var(--body-text);
            transition: background 0.4s ease, color 0.4s ease;
        }

        .container { max-width: 1200px; margin: 0 auto; }

        /* ── Header row ─────────────────────────────────────────────────── */
        .header-row {
            display: flex;
            align-items: center;
            justify-content: center;
            position: relative;
            margin-bottom: 10px;
            padding: 8px 16px;
            border-radius: 16px;
            background: var(--panel-bg);
            border: 1px solid var(--panel-border);
            backdrop-filter: blur(10px);
            box-shadow: var(--panel-shadow), 0 0 60px rgba(0,180,255,0.06);
            overflow: hidden;
        }

        .header-row::before {
            content: '';
            position: absolute;
            inset: 0;
            background: repeating-linear-gradient(
                0deg,
                transparent,
                transparent 3px,
                rgba(0,212,255,0.012) 3px,
                rgba(0,212,255,0.012) 4px
            );
            pointer-events: none;
            border-radius: 16px;
        }

        h1 {
            color: var(--accent);
            font-weight: 300;
            letter-spacing: 2px;
            text-shadow: 0 0 20px rgba(0,180,255,0.25);
            transition: color 0.4s ease;
        }

        /* ── Theme toggle ───────────────────────────────────────────────── */
        .theme-toggle {
            position: absolute;
            right: 0;
            display: flex;
            align-items: center;
            gap: 8px;
            background: var(--panel-bg);
            border: 1px solid var(--panel-border);
            border-radius: 20px;
            padding: 5px 10px 5px 10px;
            cursor: pointer;
            user-select: none;
            transition: background 0.3s, border-color 0.3s;
        }

        .theme-toggle:hover { border-color: var(--accent); }

        .theme-toggle-icon { font-size: 16px; line-height: 1; }

        .theme-toggle-label { display: none; }

        /* ── Panels ─────────────────────────────────────────────────────── */
        .panel {
            background: var(--panel-bg);
            border: 1px solid var(--panel-border);
            border-radius: 12px;
            padding: 20px;
            margin-bottom: 10px;
            backdrop-filter: blur(10px);
            box-shadow: var(--panel-shadow);
            transition: background 0.4s ease, border-color 0.4s ease;
        }

        .panel-title {
            font-size: 14px;
            color: var(--accent);
            margin-bottom: 15px;
            text-transform: uppercase;
            letter-spacing: 1px;
            font-weight: 600;
        }

        /* ── Layout helpers ─────────────────────────────────────────────── */
        .connection-row {
            display: flex; flex-wrap: wrap; gap: 15px;
            align-items: end; justify-content: center;
        }

        .input-group { display: flex; flex-direction: column; gap: 5px; }

        .input-group label {
            font-size: 12px;
            color: var(--label-text);
            font-weight: 500;
        }

        /* ── Inputs & selects ───────────────────────────────────────────── */
        select, input[type="text"], input[type="file"], input[type="number"] {
            background: var(--input-bg);
            border: 1px solid var(--input-border);
            color: var(--input-text);
            padding: 8px 12px;
            border-radius: 6px;
            font-size: 14px;
            min-width: 100px;
            transition: background 0.3s ease, border-color 0.3s ease,
                        box-shadow 0.3s ease;
        }

        select { cursor: pointer; }

        select option {
            background: var(--select-option-bg);
            color: var(--input-text);
        }

        select:hover, input[type="text"]:hover, input[type="number"]:hover {
            background: var(--input-bg-hover);
            border-color: var(--accent);
        }

        select:focus, input[type="text"]:focus, input[type="number"]:focus {
            outline: none;
            border-color: var(--accent);
            box-shadow: 0 0 0 3px rgba(0,180,255,0.15);
        }

        input[type="number"] {
            min-width: 80px; width: 100px; text-align: center;
        }

        /* ── Buttons ─────────────────────────────────────────────────────── */
        button {
            background: linear-gradient(135deg, var(--accent) 0%, var(--accent-dark) 100%);
            border: none;
            color: #fff;
            padding: 10px 24px;
            border-radius: 6px;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            text-transform: uppercase;
            font-size: 12px;
            letter-spacing: 0.5px;
        }

        button:hover:not(:disabled) {
            transform: translateY(-2px);
            box-shadow: 0 5px 20px rgba(0,180,255,0.4);
        }

        button:disabled { opacity: 0.5; cursor: not-allowed; }

        button.secondary {
            background: var(--btn-secondary-bg);
            color: var(--btn-secondary-fg);
            border: 1px solid var(--btn-secondary-bdr);
        }

        button.secondary:hover:not(:disabled) {
            background: var(--input-bg-hover);
            box-shadow: 0 5px 20px rgba(0,180,255,0.15);
        }

        button.danger {
            background: linear-gradient(135deg, #ff4757 0%, #cc0033 100%);
            color: white;
        }

        button.danger:hover:not(:disabled) {
            box-shadow: 0 5px 20px rgba(255,71,87,0.4);
        }

        /* ── Send section ────────────────────────────────────────────────── */
        .send-section { display: flex; flex-direction: column; gap: 15px; }

        .send-row { display: flex; gap: 10px; align-items: center; }
        .send-row input[type="text"] { flex: 1; }

        .line-ending { display: flex; gap: 20px; align-items: center; flex-wrap: wrap; }

        .radio-group { display: flex; align-items: center; gap: 8px; cursor: pointer; }
        .radio-group input[type="radio"] { accent-color: var(--accent); }
        .radio-group label { color: var(--label-text); font-size: 13px; cursor: pointer; }

        .json-section { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
        .json-section input[type="text"] { flex: 1; min-width: 150px; }

        /* ── Terminal tabs ───────────────────────────────────────────────── */
        .terminal-tabs {
            display: flex; gap: 20px; margin-bottom: 10px;
            align-items: center; flex-wrap: wrap;
        }

        .tab-buttons { display: flex; gap: 5px; }

        .tab-btn {
            background: transparent;
            border: none;
            color: var(--tab-inactive);
            padding: 8px 16px;
            cursor: pointer;
            font-size: 13px;
            font-weight: 600;
            text-transform: uppercase;
            letter-spacing: 0.5px;
            border-bottom: 2px solid transparent;
            transition: all 0.3s ease;
        }

        .tab-btn:hover  { color: var(--accent); }
        .tab-btn.active { color: var(--accent); border-bottom-color: var(--accent); }

        .timing-control {
            display: flex; align-items: center; gap: 8px;
            margin-left: auto; font-size: 13px; color: var(--label-text);
        }

        .timing-control input[type="checkbox"] {
            accent-color: var(--accent); width: 16px; height: 16px;
        }

        /* ── Terminal body ───────────────────────────────────────────────── */
        .terminal-container {
            border: 1px solid var(--terminal-border);
            border-radius: 8px;
            overflow: hidden;
            background: var(--terminal-bg);
            transition: background 0.4s, border-color 0.4s;
        }

        .terminal-header {
            background: var(--panel-bg);
            padding: 10px 15px;
            display: flex;
            justify-content: space-between;
            align-items: center;
            border-bottom: 1px solid var(--terminal-border);
        }

        .terminal-title { font-size: 13px; color: var(--accent); font-weight: 600; }

        .terminal-controls { display: flex; gap: 10px; align-items: center; }

        .checkbox-group { display: flex; align-items: center; gap: 6px; cursor: pointer; }
        .checkbox-group input[type="checkbox"] { accent-color: var(--accent); }
        .checkbox-group label { font-size: 12px; color: var(--label-text); cursor: pointer; }

        .terminal-body {
            height: 300px;
            overflow-y: auto;
            padding: 15px;
            font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
            font-size: 13px;
            line-height: 1.6;
            display: none;
        }

        .terminal-body.active { display: block; }

        .log-entry { margin-bottom: 4px; display: flex; gap: 10px; }

        .timestamp { color: var(--timestamp-color); min-width: 85px; }

        .direction { font-weight: bold; min-width: 20px; }
        .direction.rx { color: var(--accent); }
        .direction.tx { color: #ff6b6b; }

        .data { color: var(--body-text); word-break: break-all; }
        .data.hex { color: var(--data-hex-color); }
        .ascii-view .data { color: var(--data-ascii-color); }

        /* ── Status bar ──────────────────────────────────────────────────── */
        .status-bar {
            position: fixed; bottom: 0; left: 0; right: 0;
            background: var(--statusbar-bg);
            padding: 10px 20px;
            display: flex; justify-content: space-between; align-items: center;
            border-top: 1px solid var(--statusbar-border);
            font-size: 12px; z-index: 100;
            transition: background 0.4s, border-color 0.4s;
        }

        .status-indicator { display: flex; align-items: center; gap: 8px; }

        .status-dot {
            width: 8px; height: 8px; border-radius: 50%;
            background: #ff4757; box-shadow: 0 0 10px #ff4757;
            transition: all 0.3s ease;
        }

        .status-dot.connected { background: #2ed573; box-shadow: 0 0 10px #2ed573; }

        .stats { display: flex; gap: 20px; color: var(--label-text); }
        .stat  { display: flex; gap: 5px; }
        .stat-value { color: var(--accent); font-weight: 600; }

        /* ── Scrollbars ──────────────────────────────────────────────────── */
        ::-webkit-scrollbar { width: 8px; height: 8px; }
        ::-webkit-scrollbar-track  { background: var(--scrollbar-track); }
        ::-webkit-scrollbar-thumb  { background: var(--scrollbar-thumb); border-radius: 4px; }
        ::-webkit-scrollbar-thumb:hover { background: var(--scrollbar-hover); }

        /* ── Day theme header adjustments ───────────────────────────────── */
        body.day .header-row {
            box-shadow: var(--panel-shadow), 0 0 60px rgba(0,100,180,0.08);
        }
        body.day .header-row::before {
            background: repeating-linear-gradient(
                0deg,
                transparent,
                transparent 3px,
                rgba(0,100,180,0.018) 3px,
                rgba(0,100,180,0.018) 4px
            );
        }

        /* ── Responsive ──────────────────────────────────────────────────── */
        @media (max-width: 768px) {
            .connection-row { flex-direction: column; align-items: stretch; }
            .input-group { width: 100%; }
            select, input[type="text"] { width: 100%; }
            .terminal-tabs { flex-direction: column; align-items: flex-start; }
            .timing-control { margin-left: 0; margin-top: 10px; }
            .theme-toggle { position: static; margin-left: auto; }
            .header-row { flex-wrap: wrap; gap: 10px; }
        }