:root {
            --bg-color: #090b10;
            --panel: #11151d;
            --panel-strong: #151b26;
            --field: #090d14;
            --field-raised: #0e1420;
            --text-primary: #f8fafc;
            --text-secondary: #9aa7b8;
            --text-muted: #687589;
            --accent: #19c6b3;
            --accent-hover: #5eead4;
            --accent-soft: rgba(25, 198, 179, 0.13);
            --accent-soft2: rgba(25, 198, 179, 0.07);
            --amber: #f5b84b;
            --amber-soft: rgba(245, 184, 75, 0.12);
            --coral: #f07167;
            --coral-soft: rgba(240, 113, 103, 0.12);
            --border: rgba(148, 163, 184, 0.18);
            --border-strong: rgba(148, 163, 184, 0.28);
            --shadow: 0 30px 90px rgba(0, 0, 0, 0.42);
        }

        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            -webkit-tap-highlight-color: transparent;
        }

        body {
            background:
                linear-gradient(135deg, rgba(25, 198, 179, 0.16), transparent 34%),
                linear-gradient(315deg, rgba(240, 113, 103, 0.13), transparent 32%),
                linear-gradient(180deg, #10131b 0%, var(--bg-color) 64%);
            color: var(--text-primary);
            font-family: Inter, 'Segoe UI', system-ui, -apple-system, sans-serif;
            min-height: 100vh;
            display: flex;
            justify-content: center;
            align-items: flex-start;
            padding: 18px;
            padding-top: max(18px, env(safe-area-inset-top));
            padding-bottom: max(36px, env(safe-area-inset-bottom));
        }

        .container {
            background:
                linear-gradient(180deg, rgba(255, 255, 255, 0.05), transparent 42%),
                var(--panel);
            border: 1px solid var(--border);
            border-radius: 8px;
            box-shadow: var(--shadow);
            width: 100%;
            max-width: 960px;
            overflow: hidden;
            position: relative;
        }

        .container::before {
            content: "";
            position: absolute;
            inset: 0 0 auto;
            height: 3px;
            background: linear-gradient(90deg, var(--accent), var(--amber), var(--coral));
        }

        header {
            align-items: flex-start;
            border-bottom: 1px solid var(--border);
            display: grid;
            grid-template-columns: auto minmax(0, 1fr) auto;
            justify-content: initial;
            gap: 1rem;
            padding: 1.35rem 1.5rem 1.1rem;
        }

        .back-btn {
            align-items: center;
            align-self: flex-start;
            background: var(--field-raised);
            border: 1px solid var(--border);
            border-radius: 8px;
            color: var(--text-secondary);
            display: inline-flex;
            height: 38px;
            justify-content: center;
            text-decoration: none;
            transition: background-color 0.18s, border-color 0.18s, color 0.18s;
            width: 38px;
        }

        .back-btn:hover,
        .back-btn:focus-visible {
            background: var(--accent-soft);
            border-color: rgba(94, 234, 212, 0.38);
            color: var(--accent-hover);
        }

        .back-btn:focus-visible {
            outline: 3px solid rgba(94, 234, 212, 0.28);
            outline-offset: 3px;
        }

        .back-btn svg {
            height: 18px;
            width: 18px;
        }

        h1 {
            color: var(--text-primary);
            font-size: 1.6rem;
            font-weight: 760;
            letter-spacing: 0;
            line-height: 1.12;
            margin-bottom: 0.38rem;
        }

        p.subtitle {
            color: var(--text-secondary);
            font-size: 0.9rem;
        }

        .status-line {
            align-items: center;
            color: var(--text-muted);
            display: flex;
            flex: 0 0 auto;
            font-size: 0.82rem;
            gap: 0.45rem;
            min-height: 1.25rem;
            padding-top: 0.15rem;
            white-space: nowrap;
        }

        .status-dot {
            background: var(--accent);
            border-radius: 50%;
            box-shadow: 0 0 0 4px rgba(25, 198, 179, 0.12);
            height: 7px;
            width: 7px;
            flex-shrink: 0;
        }

        /* Tab Navigation */
        .tab-nav {
            display: flex;
            gap: 0;
            border-bottom: 1px solid var(--border);
            padding: 0 1.5rem;
            overflow-x: auto;
            scrollbar-width: none;
        }

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

        .tab-btn {
            background: none;
            border: none;
            border-bottom: 2px solid transparent;
            color: var(--text-muted);
            cursor: pointer;
            font: inherit;
            font-size: 0.8rem;
            font-weight: 700;
            letter-spacing: 0.03em;
            padding: 0.85rem 1rem;
            text-transform: uppercase;
            transition: color 0.18s, border-color 0.18s;
            white-space: nowrap;
            margin-bottom: -1px;
        }

        .tab-btn:hover {
            color: var(--text-secondary);
        }

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

        /* Content panels */
        .tab-panel {
            display: none;
            padding: 1.25rem;
        }

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

        /* Section grid */
        .section-grid {
            display: grid;
            gap: 1rem;
            grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
        }

        .section-grid.two-col {
            grid-template-columns: repeat(auto-fill, minmax(380px, 1fr));
        }

        .section-grid.full {
            grid-template-columns: 1fr;
        }

        /* Cards */
        .card {
            background:
                linear-gradient(180deg, rgba(255, 255, 255, 0.035), transparent),
                var(--panel-strong);
            border: 1px solid var(--border);
            border-radius: 8px;
            padding: 1rem;
            position: relative;
        }

        .card-title {
            color: var(--text-secondary);
            font-size: 0.72rem;
            font-weight: 760;
            letter-spacing: 0.06em;
            text-transform: uppercase;
            margin-bottom: 0.85rem;
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        .card-title-dot {
            width: 6px;
            height: 6px;
            border-radius: 50%;
            flex-shrink: 0;
        }

        .dot-accent {
            background: var(--accent);
        }

        .dot-amber {
            background: var(--amber);
        }

        .dot-coral {
            background: var(--coral);
        }

        /* Identity / law rows */
        .law-list {
            display: flex;
            flex-direction: column;
            gap: 0.45rem;
        }

        .law-row {
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 0.75rem;
            background: var(--field);
            border: 1px solid var(--border);
            border-radius: 6px;
            padding: 0.55rem 0.8rem;
            transition: border-color 0.18s, background-color 0.18s;
            cursor: default;
        }

        .law-row:hover {
            border-color: rgba(94, 234, 212, 0.28);
            background: var(--field-raised);
        }

        .law-name {
            color: var(--text-muted);
            font-size: 0.73rem;
            font-weight: 600;
            min-width: 90px;
            flex-shrink: 0;
        }

        .law-expr {
            font-family: 'Cascadia Mono', 'SFMono-Regular', Consolas, 'Courier New', monospace;
            font-size: 0.92rem;
            font-weight: 650;
            color: var(--accent-hover);
            text-align: right;
            flex: 1;
        }

        .law-expr .op-and {
            color: var(--amber);
        }

        .law-expr .op-or {
            color: var(--coral);
        }

        .law-expr .op-not {
            color: #a78bfa;
        }

        .law-expr .op-xor {
            color: #60a5fa;
        }

        .law-expr .val-1 {
            color: var(--accent-hover);
        }

        .law-expr .val-0 {
            color: var(--text-muted);
        }

        /* Truth tables */
        .truth-table {
            width: 100%;
            border-collapse: collapse;
            font-family: 'Cascadia Mono', 'SFMono-Regular', Consolas, 'Courier New', monospace;
            font-size: 0.88rem;
        }

        .truth-table thead th {
            background: var(--field);
            border: 1px solid var(--border);
            color: var(--text-secondary);
            font-size: 0.72rem;
            font-weight: 760;
            letter-spacing: 0.05em;
            padding: 0.5rem 0.7rem;
            text-align: center;
            text-transform: uppercase;
        }

        .truth-table tbody td {
            border: 1px solid var(--border);
            padding: 0.45rem 0.7rem;
            text-align: center;
            background: var(--field-raised);
            transition: background-color 0.15s;
        }

        .truth-table tbody tr:hover td {
            background: rgba(25, 198, 179, 0.06);
        }

        .truth-table .v1 {
            color: var(--accent-hover);
            font-weight: 700;
        }

        .truth-table .v0 {
            color: var(--text-muted);
        }

        .truth-table thead th.result-col {
            color: var(--amber);
        }

        /* Gate symbol cards */
        .gates-grid {
            display: grid;
            gap: 1rem;
            grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
        }

        .gate-card {
            background:
                linear-gradient(180deg, rgba(255, 255, 255, 0.035), transparent),
                var(--panel-strong);
            border: 1px solid var(--border);
            border-radius: 8px;
            padding: 1rem;
        }

        .gate-card-header {
            display: flex;
            align-items: center;
            justify-content: space-between;
            margin-bottom: 0.75rem;
        }

        .gate-name {
            font-size: 0.85rem;
            font-weight: 760;
            color: var(--text-primary);
        }

        .gate-symbol-badge {
            font-family: 'Cascadia Mono', 'SFMono-Regular', Consolas, 'Courier New', monospace;
            font-size: 0.75rem;
            font-weight: 700;
            padding: 0.25rem 0.6rem;
            border-radius: 4px;
            background: var(--accent-soft);
            color: var(--accent-hover);
            border: 1px solid rgba(94, 234, 212, 0.22);
        }

        .gate-symbol-badge.amber {
            background: var(--amber-soft);
            color: var(--amber);
            border-color: rgba(245, 184, 75, 0.22);
        }

        .gate-symbol-badge.coral {
            background: var(--coral-soft);
            color: var(--coral);
            border-color: rgba(240, 113, 103, 0.22);
        }

        .gate-symbol-badge.violet {
            background: rgba(167, 139, 250, 0.12);
            color: #a78bfa;
            border-color: rgba(167, 139, 250, 0.22);
        }

        .gate-symbol-badge.blue {
            background: rgba(96, 165, 250, 0.12);
            color: #60a5fa;
            border-color: rgba(96, 165, 250, 0.22);
        }

        .gate-expr {
            font-family: 'Cascadia Mono', 'SFMono-Regular', Consolas, 'Courier New', monospace;
            font-size: 0.88rem;
            color: var(--text-secondary);
            margin-bottom: 0.75rem;
        }

        /* Inline truth table inside gate card */
        .mini-table {
            width: 100%;
            border-collapse: collapse;
            font-family: 'Cascadia Mono', 'SFMono-Regular', Consolas, 'Courier New', monospace;
            font-size: 0.82rem;
        }

        .mini-table th {
            background: var(--field);
            border: 1px solid var(--border);
            color: var(--text-muted);
            font-size: 0.68rem;
            font-weight: 760;
            padding: 0.35rem 0.5rem;
            text-align: center;
            letter-spacing: 0.04em;
            text-transform: uppercase;
        }

        .mini-table td {
            border: 1px solid var(--border);
            background: var(--field-raised);
            padding: 0.32rem 0.5rem;
            text-align: center;
        }

        .mini-table .v1 {
            color: var(--accent-hover);
            font-weight: 700;
        }

        .mini-table .v0 {
            color: var(--text-muted);
        }

        .mini-table th.r {
            color: var(--amber);
        }

        /* DeMorgan section */
        .demorgan-row {
            background: var(--field);
            border: 1px solid var(--border);
            border-radius: 6px;
            padding: 0.7rem 0.9rem;
            margin-bottom: 0.5rem;
            transition: border-color 0.18s;
        }

        .demorgan-row:hover {
            border-color: rgba(94, 234, 212, 0.28);
        }

        .demorgan-label {
            font-size: 0.69rem;
            font-weight: 700;
            color: var(--text-muted);
            text-transform: uppercase;
            letter-spacing: 0.06em;
            margin-bottom: 0.3rem;
        }

        .demorgan-expr {
            font-family: 'Cascadia Mono', 'SFMono-Regular', Consolas, 'Courier New', monospace;
            font-size: 1.05rem;
            font-weight: 650;
            color: var(--accent-hover);
        }

        .demorgan-eq {
            color: var(--text-muted);
            margin: 0 0.4rem;
        }

        /* SOP / POS */
        .form-block {
            background: var(--field);
            border: 1px solid var(--border);
            border-radius: 6px;
            padding: 0.75rem 0.9rem;
            margin-bottom: 0.5rem;
        }

        .form-block-label {
            font-size: 0.69rem;
            font-weight: 760;
            text-transform: uppercase;
            letter-spacing: 0.06em;
            margin-bottom: 0.35rem;
        }

        .form-block-label.amber {
            color: var(--amber);
        }

        .form-block-label.coral {
            color: var(--coral);
        }

        .form-block-expr {
            font-family: 'Cascadia Mono', 'SFMono-Regular', Consolas, 'Courier New', monospace;
            font-size: 0.9rem;
            color: var(--text-primary);
            line-height: 1.6;
        }

        .form-block-desc {
            font-size: 0.76rem;
            color: var(--text-muted);
            margin-top: 0.35rem;
        }

        /* Karnaugh map */
        .kmap-wrapper {
            overflow-x: auto;
        }

        .kmap-table {
            border-collapse: collapse;
            font-family: 'Cascadia Mono', 'SFMono-Regular', Consolas, 'Courier New', monospace;
            font-size: 0.85rem;
            margin: 0 auto;
        }

        .kmap-table th,
        .kmap-table td {
            border: 1px solid var(--border);
            text-align: center;
            min-width: 46px;
            height: 40px;
            padding: 0.3rem;
        }

        .kmap-table th {
            background: var(--field);
            color: var(--text-secondary);
            font-size: 0.72rem;
            font-weight: 760;
            letter-spacing: 0.04em;
        }

        .kmap-table td {
            background: var(--field-raised);
            color: var(--text-muted);
            cursor: pointer;
            transition: background-color 0.15s, color 0.15s;
        }

        .kmap-table td.v1 {
            color: var(--accent-hover);
            font-weight: 700;
            background: var(--accent-soft2);
        }

        .kmap-table td:hover {
            background: rgba(25, 198, 179, 0.1);
            border-color: rgba(94, 234, 212, 0.35);
        }

        .kmap-axis-label {
            font-size: 0.74rem;
            color: var(--text-muted);
            text-align: center;
            margin-top: 0.5rem;
        }

        .kmap-hint {
            font-size: 0.75rem;
            color: var(--text-muted);
            margin-top: 0.6rem;
            text-align: center;
        }

        /* Operator precedence */
        .precedence-list {
            display: flex;
            flex-direction: column;
            gap: 0.4rem;
        }

        .prec-row {
            display: flex;
            align-items: center;
            gap: 0.75rem;
            background: var(--field);
            border: 1px solid var(--border);
            border-radius: 6px;
            padding: 0.5rem 0.8rem;
        }

        .prec-rank {
            font-size: 0.68rem;
            font-weight: 760;
            color: var(--text-muted);
            min-width: 26px;
            border: 1px solid var(--border);
            border-radius: 4px;
            text-align: center;
            padding: 0.15rem 0.3rem;
        }

        .prec-op {
            font-family: 'Cascadia Mono', 'SFMono-Regular', Consolas, 'Courier New', monospace;
            font-size: 0.9rem;
            font-weight: 700;
            min-width: 60px;
        }

        .prec-desc {
            font-size: 0.78rem;
            color: var(--text-muted);
        }

        .prec-op.accent {
            color: var(--accent-hover);
        }

        .prec-op.amber {
            color: var(--amber);
        }

        .prec-op.coral {
            color: var(--coral);
        }

        .prec-op.violet {
            color: #a78bfa;
        }

        .prec-op.blue {
            color: #60a5fa;
        }

        /* Notation comparison */
        .notation-table {
            width: 100%;
            border-collapse: collapse;
            font-size: 0.84rem;
        }

        .notation-table th {
            background: var(--field);
            border: 1px solid var(--border);
            color: var(--text-secondary);
            font-size: 0.7rem;
            font-weight: 760;
            letter-spacing: 0.05em;
            padding: 0.5rem 0.7rem;
            text-align: center;
            text-transform: uppercase;
        }

        .notation-table td {
            border: 1px solid var(--border);
            background: var(--field-raised);
            padding: 0.35rem 0.7rem;
            text-align: center;
            font-family: 'Cascadia Mono', 'SFMono-Regular', Consolas, 'Courier New', monospace;
            font-size: 0.85rem;
            transition: background-color 0.15s;
            vertical-align: middle;
        }

        .notation-table tr:hover td {
            background: rgba(25, 198, 179, 0.06);
        }

        .notation-table .op-name {
            font-family: inherit;
            font-size: 0.8rem;
            color: var(--text-secondary);
            font-weight: 600;
        }

        @media (max-width: 760px) {
            body {
                align-items: flex-start;
            }

            header {
                display: block;
                padding: 1.2rem 1rem 1rem;
            }

            .status-line {
                margin-top: 0.85rem;
            }

            h1 {
                font-size: 1.35rem;
            }

            .tab-nav {
                padding: 0 1rem;
            }

            .tab-panel {
                padding: 1rem;
            }

            .section-grid,
            .section-grid.two-col {
                grid-template-columns: 1fr;
            }

            .gates-grid {
                grid-template-columns: 1fr;
            }

            .back-btn {
                display: none;
            }
        }

        @media (max-width: 420px) {
            body {
                padding-left: 12px;
                padding-right: 12px;
            }

            .tab-btn {
                font-size: 0.72rem;
                padding: 0.75rem 0.65rem;
            }
        }