/* ============================================================
   LINEAR CONTROL VALVE – VIRTUAL LABORATORY
   Design System & Styles
   ============================================================ */

/* ── CSS Custom Properties ──────────────────────────────── */
:root {
    /* Palette */
    --bg-primary:      #0a0e1a;
    --bg-secondary:    #111827;
    --bg-card:         #1a1f35;
    --bg-card-hover:   #1f2545;
    --bg-elevated:     #232a47;

    --text-primary:    #f0f2f8;
    --text-secondary:  #94a3c0;
    --text-muted:      #5e6b86;
    --text-accent:     #60a5fa;

    --accent-blue:     #3b82f6;
    --accent-blue-glow:#3b82f640;
    --accent-cyan:     #22d3ee;
    --accent-green:    #10b981;
    --accent-green-glow:#10b98140;
    --accent-amber:    #f59e0b;
    --accent-red:      #ef4444;
    --accent-red-glow: #ef444440;
    --accent-purple:   #a78bfa;
    --accent-purple-glow:#a78bfa40;

    --border-subtle:   #1e2a4a;
    --border-active:   #3b82f680;

    --water-blue:      #38bdf8;
    --water-blue-dark: #0284c7;
    --pipe-gray:       #4b5563;
    --metal-light:     #9ca3af;
    --metal-dark:      #6b7280;

    /* Spacing */
    --space-xs:   4px;
    --space-sm:   8px;
    --space-md:   16px;
    --space-lg:   24px;
    --space-xl:   32px;
    --space-2xl:  48px;

    /* Radius */
    --radius-sm:  6px;
    --radius-md:  10px;
    --radius-lg:  14px;
    --radius-xl:  20px;

    /* Typography */
    --font-sans:  'Inter', system-ui, -apple-system, sans-serif;
    --font-mono:  'JetBrains Mono', 'Fira Code', monospace;

    /* Transitions */
    --transition-fast:   150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base:   250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-smooth: 400ms cubic-bezier(0.22, 1, 0.36, 1);
}

/* ── Reset & Base ───────────────────────────────────────── */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-sans);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
}

/* ── Background Texture ─────────────────────────────────── */
body::before {
    content: '';
    position: fixed;
    inset: 0;
    background:
        radial-gradient(ellipse 80% 60% at 20% 10%, #3b82f608 0%, transparent 70%),
        radial-gradient(ellipse 60% 50% at 80% 90%, #a78bfa06 0%, transparent 70%);
    pointer-events: none;
    z-index: 0;
}

/* ── Header ─────────────────────────────────────────────── */
#lab-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: linear-gradient(180deg, #0f1429ee 0%, #111827ee 100%);
    backdrop-filter: blur(20px) saturate(1.4);
    border-bottom: 1px solid var(--border-subtle);
}

.header-glow {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 1px;
    background: linear-gradient(90deg, transparent 0%, var(--accent-blue) 30%, var(--accent-purple) 70%, transparent 100%);
    opacity: 0.6;
}

.header-content {
    max-width: 1600px;
    margin: 0 auto;
    padding: var(--space-md) var(--space-xl);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.header-left {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.lab-icon svg {
    width: 40px;
    height: 40px;
}

.header-text h1 {
    font-size: 1.1rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    background: linear-gradient(135deg, var(--text-primary), var(--text-secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.header-subtitle {
    font-size: 0.78rem;
    color: var(--accent-blue);
    font-weight: 500;
    margin-top: 2px;
    letter-spacing: 0.02em;
}

.status-badge {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: 6px 14px;
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: 20px;
    font-size: 0.78rem;
    font-weight: 500;
    color: var(--text-secondary);
    transition: var(--transition-base);
}

.status-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--text-muted);
    transition: var(--transition-base);
}

.status-badge.running {
    border-color: var(--accent-green-glow);
    color: var(--accent-green);
}

.status-badge.running .status-dot {
    background: var(--accent-green);
    box-shadow: 0 0 8px var(--accent-green-glow);
    animation: pulse-dot 1.5s ease-in-out infinite;
}

.status-badge.stopped {
    border-color: var(--accent-red-glow);
    color: var(--accent-red);
}

.status-badge.stopped .status-dot {
    background: var(--accent-red);
}

@keyframes pulse-dot {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.4; }
}

/* ── Main Layout ────────────────────────────────────────── */
#lab-main {
    max-width: 1600px;
    margin: 0 auto;
    padding: var(--space-xl);
    position: relative;
    z-index: 1;
}

.top-section {
    display: grid;
    grid-template-columns: 1fr 420px;
    gap: var(--space-xl);
    margin-bottom: var(--space-xl);
}

/* ── Panel Base ─────────────────────────────────────────── */
.panel {
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    overflow: hidden;
    transition: border-color var(--transition-base);
}

.panel:hover {
    border-color: #2a3560;
}

.panel-header {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-md) var(--space-lg);
    border-bottom: 1px solid var(--border-subtle);
    background: linear-gradient(180deg, #1e2545 0%, transparent 100%);
}

.panel-icon {
    width: 20px;
    height: 20px;
    color: var(--accent-blue);
    flex-shrink: 0;
}

.panel-icon svg {
    width: 100%;
    height: 100%;
}

.panel-header h2 {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-primary);
    letter-spacing: -0.01em;
}

.panel-badge {
    margin-left: auto;
    padding: 2px 10px;
    background: var(--accent-blue);
    background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
    color: white;
    font-size: 0.65rem;
    font-weight: 600;
    border-radius: 10px;
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

/* ── Diagram Panel ──────────────────────────────────────── */
.diagram-panel {
    min-height: 520px;
}

.diagram-container {
    padding: var(--space-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 480px;
}

.diagram-container svg {
    width: 100%;
    height: 100%;
    max-height: 480px;
}

/* ── Controls ───────────────────────────────────────────── */
.controls-column {
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
}

.controls-content {
    padding: var(--space-lg);
}

/* Buttons */
.button-group {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-sm);
}

.btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: 10px 16px;
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
    background: var(--bg-elevated);
    color: var(--text-primary);
    font-family: var(--font-sans);
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
}

.btn svg {
    width: 16px;
    height: 16px;
    flex-shrink: 0;
}

.btn:hover:not(:disabled) {
    transform: translateY(-1px);
}

.btn:active:not(:disabled) {
    transform: translateY(0);
}

.btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

.btn-start {
    grid-column: 1 / -1;
    background: linear-gradient(135deg, #059669, #10b981);
    border-color: #10b98150;
    color: white;
    padding: 12px 16px;
    font-size: 0.85rem;
}

.btn-start:hover:not(:disabled) {
    box-shadow: 0 4px 20px var(--accent-green-glow);
}

.btn-start.running {
    background: linear-gradient(135deg, #0d7a5f, #0e9f6e);
    animation: btn-pulse 2s ease-in-out infinite;
}

@keyframes btn-pulse {
    0%, 100% { box-shadow: 0 0 0 0 var(--accent-green-glow); }
    50% { box-shadow: 0 0 20px 4px var(--accent-green-glow); }
}

.btn-stop {
    background: linear-gradient(135deg, #b91c1c, #ef4444);
    border-color: #ef444450;
    color: white;
}

.btn-stop:hover:not(:disabled) {
    box-shadow: 0 4px 20px var(--accent-red-glow);
}

.btn-reset {
    background: var(--bg-elevated);
    border-color: var(--border-subtle);
}

.btn-reset:hover:not(:disabled) {
    background: var(--bg-card-hover);
    border-color: var(--accent-blue);
}

.btn-construction {
    width: 100%;
    background: var(--bg-elevated);
    border-color: var(--border-subtle);
    color: var(--accent-purple);
}

.btn-construction:hover {
    border-color: var(--accent-purple);
    box-shadow: 0 2px 12px var(--accent-purple-glow);
}

.divider {
    height: 1px;
    background: var(--border-subtle);
    margin: var(--space-md) 0;
}

/* Slider */
.slider-section {
    margin-top: var(--space-sm);
}

.slider-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--space-md);
}

.slider-header label {
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.slider-value-display {
    display: flex;
    align-items: baseline;
    gap: 2px;
    background: var(--bg-primary);
    padding: 4px 12px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-subtle);
}

.slider-value {
    font-family: var(--font-mono);
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--accent-cyan);
}

.slider-unit {
    font-size: 0.7rem;
    color: var(--text-muted);
    font-weight: 500;
}

.slider-wrapper {
    position: relative;
    height: 36px;
    display: flex;
    align-items: center;
}

input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 6px;
    background: var(--bg-primary);
    border-radius: 3px;
    outline: none;
    position: relative;
    z-index: 2;
    border: 1px solid var(--border-subtle);
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--accent-cyan), var(--accent-blue));
    cursor: pointer;
    border: 3px solid var(--bg-card);
    box-shadow: 0 2px 8px rgba(34, 211, 238, 0.3);
    transition: box-shadow var(--transition-fast);
}

input[type="range"]::-webkit-slider-thumb:hover {
    box-shadow: 0 2px 16px rgba(34, 211, 238, 0.5);
}

input[type="range"]:disabled::-webkit-slider-thumb {
    background: var(--metal-dark);
    cursor: not-allowed;
    box-shadow: none;
}

input[type="range"]::-moz-range-thumb {
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--accent-cyan), var(--accent-blue));
    cursor: pointer;
    border: 3px solid var(--bg-card);
    box-shadow: 0 2px 8px rgba(34, 211, 238, 0.3);
}

.slider-track-fill {
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    height: 6px;
    background: linear-gradient(90deg, var(--accent-cyan), var(--accent-blue));
    border-radius: 3px;
    pointer-events: none;
    z-index: 1;
    width: 0%;
    transition: width 50ms linear;
}

.slider-marks {
    display: flex;
    justify-content: space-between;
    margin-top: var(--space-xs);
    font-size: 0.65rem;
    color: var(--text-muted);
    font-family: var(--font-mono);
}

/* ── Readings Panel ─────────────────────────────────────── */
.readings-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-sm);
    padding: var(--space-md);
}

.reading-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
    padding: var(--space-md);
    transition: border-color var(--transition-base);
}

.reading-card:hover {
    border-color: #2a3560;
}

.reading-label {
    font-size: 0.7rem;
    font-weight: 500;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    margin-bottom: var(--space-xs);
}

.reading-value {
    font-family: var(--font-mono);
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent-cyan);
}

.reading-value .reading-unit {
    font-size: 0.7rem;
    color: var(--text-muted);
    margin-left: 2px;
}

.flow-highlight {
    color: var(--accent-green);
}

.reading-bar {
    margin-top: var(--space-sm);
    height: 4px;
    background: var(--bg-elevated);
    border-radius: 2px;
    overflow: hidden;
}

.reading-bar-fill {
    height: 100%;
    border-radius: 2px;
    transition: width 200ms ease-out;
    width: 0%;
}

.valve-bar {
    background: linear-gradient(90deg, var(--accent-cyan), var(--accent-blue));
}

.flow-bar {
    background: linear-gradient(90deg, var(--accent-green), var(--accent-cyan));
}

.reading-status {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    margin-top: var(--space-xs);
}

.status-indicator {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    display: inline-block;
}

.status-indicator.off {
    background: var(--text-muted);
}

.status-indicator.on {
    background: var(--accent-green);
    box-shadow: 0 0 8px var(--accent-green-glow);
    animation: pulse-dot 1.5s ease-in-out infinite;
}

/* ── Tabs Section ───────────────────────────────────────── */
.bottom-section {
    margin-top: var(--space-lg);
}

.tabs-container {
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.tabs-nav {
    display: flex;
    border-bottom: 1px solid var(--border-subtle);
    background: linear-gradient(180deg, #1e2545 0%, var(--bg-card) 100%);
    overflow-x: auto;
}

.tab-btn {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: 14px 24px;
    border: none;
    background: none;
    color: var(--text-muted);
    font-family: var(--font-sans);
    font-size: 0.82rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-base);
    border-bottom: 2px solid transparent;
    white-space: nowrap;
}

.tab-btn svg {
    width: 16px;
    height: 16px;
    flex-shrink: 0;
}

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

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

.tab-content {
    display: none;
    padding: var(--space-xl);
    animation: fadeInTab 300ms ease;
}

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

@keyframes fadeInTab {
    from { opacity: 0; transform: translateY(8px); }
    to   { opacity: 1; transform: translateY(0); }
}

/* ── Graph ──────────────────────────────────────────────── */
.graph-container {
    max-width: 900px;
    margin: 0 auto;
    height: 420px;
    position: relative;
}

.graph-container canvas {
    width: 100% !important;
    height: 100% !important;
}

/* ── Observation Table ──────────────────────────────────── */
.table-container {
    overflow-x: auto;
}

#observationTable {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    font-size: 0.85rem;
}

#observationTable thead th {
    background: var(--bg-elevated);
    color: var(--text-secondary);
    font-weight: 600;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    padding: 12px 16px;
    text-align: left;
    border-bottom: 1px solid var(--border-subtle);
    position: sticky;
    top: 0;
}

#observationTable thead th:first-child {
    border-radius: var(--radius-sm) 0 0 0;
}

#observationTable thead th:last-child {
    border-radius: 0 var(--radius-sm) 0 0;
}

#observationTable tbody td {
    padding: 10px 16px;
    border-bottom: 1px solid var(--border-subtle);
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 0.82rem;
}

#observationTable tbody td:last-child {
    font-family: var(--font-sans);
    color: var(--text-secondary);
    font-size: 0.78rem;
}

#observationTable tbody tr {
    transition: background var(--transition-fast);
}

/* ── Working Principle ──────────────────────────────────── */
.principle-content {
    max-width: 1200px;
    margin: 0 auto;
}

.principle-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-lg, 1.5rem);
}

.principle-card {
    background: var(--bg-primary, #111827);
    border: 1px solid var(--border-subtle, rgba(255, 255, 255, 0.1));
    border-radius: var(--radius-md, 8px);
    padding: var(--space-lg, 1.5rem);
    display: flex;
    flex-direction: column;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.principle-card.full-width {
    grid-column: 1 / -1;
}

.principle-card h3 {
    font-size: 1.05rem;
    font-weight: 700;
    color: var(--text-primary, #f3f4f6);
    margin-bottom: var(--space-md, 1rem);
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--border-subtle, rgba(255, 255, 255, 0.1));
    letter-spacing: -0.01em;
}

.principle-card p {
    font-size: 0.88rem;
    color: var(--text-secondary, #9ca3af);
    line-height: 1.65;
    margin-bottom: var(--space-sm, 0.75rem);
}

.characteristic-detail {
    display: grid;
    grid-template-columns: 1.1fr 0.9fr;
    gap: var(--space-lg, 1.5rem);
    margin-top: var(--space-sm, 0.5rem);
}

@media (max-width: 900px) {
    .characteristic-detail {
        grid-template-columns: 1fr;
    }
}

.char-text {
    display: flex;
    flex-direction: column;
    gap: var(--space-xs, 0.5rem);
}

.char-text ul {
    margin-top: var(--space-xs, 0.5rem);
    padding-left: 1.2rem;
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.char-text ul li {
    font-size: 0.88rem;
    color: var(--text-secondary, #9ca3af);
    line-height: 1.5;
}

.formula {
    background: var(--bg-secondary, #1f2937);
    border: 1px solid var(--border-subtle, rgba(255, 255, 255, 0.1));
    border-left: 4px solid var(--accent-cyan, #38bdf8);
    border-radius: var(--radius-sm, 4px);
    padding: var(--space-md, 1rem);
    margin: var(--space-sm, 0.5rem) 0;
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
}

.formula code {
    font-family: var(--font-mono, monospace);
    font-size: 1.05rem;
    font-weight: 700;
    color: var(--accent-cyan, #38bdf8);
}

.formula .formula-note {
    font-size: 0.78rem;
    color: var(--text-muted, #6b7280);
    font-style: italic;
}

.char-comparison {
    background: var(--bg-secondary, #1f2937);
    border: 1px solid var(--border-subtle, rgba(255, 255, 255, 0.1));
    border-radius: var(--radius-md, 8px);
    padding: var(--space-md, 1rem);
    overflow-x: auto;
}

.char-comparison h4 {
    font-size: 0.88rem;
    font-weight: 600;
    color: var(--text-primary, #f3f4f6);
    margin-bottom: var(--space-sm, 0.75rem);
    text-align: center;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

.comparison-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.82rem;
    text-align: center;
}

.comparison-table th {
    background: rgba(0, 0, 0, 0.3);
    color: var(--text-muted, #9ca3af);
    font-weight: 600;
    padding: 0.6rem 0.5rem;
    border-bottom: 1px solid var(--border-subtle, rgba(255, 255, 255, 0.1));
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.comparison-table td {
    padding: 0.5rem 0.5rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
    color: var(--text-secondary, #d1d5db);
    font-family: var(--font-mono, monospace);
}

.comparison-table tr:last-child td {
    border-bottom: none;
}

.comparison-table td.highlight {
    color: var(--accent-cyan, #38bdf8);
    font-weight: 700;
    background: rgba(56, 189, 248, 0.1);
}

.principle-list {
    list-style: none;
    padding: 0;
    margin: var(--space-xs, 0.5rem) 0 0 0;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.principle-list li {
    font-size: 0.88rem;
    color: var(--text-secondary, #9ca3af);
    line-height: 1.5;
    position: relative;
    padding-left: 1.5rem;
}

.principle-list li::before {
    position: absolute;
    left: 0;
    top: 0;
    font-weight: bold;
}

.advantage-list li::before {
    content: '✓';
    color: #34d399;
}

.disadvantage-list li::before {
    content: '✕';
    color: #f87171;
}

.applications-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: var(--space-md, 1rem);
    margin-top: var(--space-md, 1rem);
}

.app-item {
    background: var(--bg-secondary, #1f2937);
    border: 1px solid var(--border-subtle, rgba(255, 255, 255, 0.1));
    border-radius: var(--radius-md, 8px);
    padding: var(--space-md, 1rem);
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    transition: transform 0.2s ease, border-color 0.2s ease;
}

.app-item:hover {
    transform: translateY(-2px);
    border-color: var(--accent-blue, #60a5fa);
}

.app-item h4 {
    font-size: 0.92rem;
    font-weight: 600;
    color: var(--text-primary, #f3f4f6);
    margin-top: 0.2rem;
}

.app-item p {
    font-size: 0.82rem;
    color: var(--text-muted, #9ca3af);
    line-height: 1.5;
    margin: 0;
}

.app-badge {
    display: inline-block;
    align-self: flex-start;
    padding: 0.2rem 0.55rem;
    border-radius: 4px;
    font-size: 0.68rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    background: rgba(56, 189, 248, 0.15);
    color: var(--accent-cyan, #38bdf8);
    border: 1px solid rgba(56, 189, 248, 0.3);
}

.app-badge.safety {
    background: rgba(251, 146, 60, 0.15);
    color: #fb923c;
    border-color: rgba(251, 146, 60, 0.3);
}

.app-badge.emergency {
    background: rgba(248, 113, 113, 0.15);
    color: #f87171;
    border-color: rgba(248, 113, 113, 0.3);
}

.app-badge.initial-flow {
    background: rgba(167, 139, 250, 0.15);
    color: #a78bfa;
    border-color: rgba(167, 139, 250, 0.3);
}

#observationTable tbody tr:hover:not(.empty-row) {
    background: var(--bg-card-hover);
}

#observationTable tbody tr.new-row {
    animation: rowAppear 400ms ease;
}

@keyframes rowAppear {
    from { background: var(--accent-blue); background: #3b82f620; }
    to   { background: transparent; }
}

.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-md);
    padding: var(--space-2xl);
    color: var(--text-muted);
}

.empty-state svg {
    width: 48px;
    height: 48px;
    opacity: 0.3;
}

.empty-state p {
    font-size: 0.85rem;
    font-family: var(--font-sans);
}

/* ── Working Principle ──────────────────────────────────── */
.principle-content {
    max-width: 1200px;
    margin: 0 auto;
}

.principle-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-lg);
}

.principle-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    padding: var(--space-xl);
    transition: border-color var(--transition-base);
}

.principle-card:hover {
    border-color: #2a3560;
}

.principle-card.full-width {
    grid-column: 1 / -1;
}

.principle-card-icon {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--space-md);
}

.principle-card-icon svg {
    width: 22px;
    height: 22px;
}

.construction-icon { background: #3b82f620; color: var(--accent-blue); }
.principle-icon    { background: #a78bfa20; color: var(--accent-purple); }
.characteristic-icon { background: #22d3ee20; color: var(--accent-cyan); }
.advantage-icon    { background: #10b98120; color: var(--accent-green); }
.disadvantage-icon { background: #ef444420; color: var(--accent-red); }
.application-icon  { background: #f59e0b20; color: var(--accent-amber); }

.principle-card h3 {
    font-size: 1.05rem;
    font-weight: 700;
    margin-bottom: var(--space-md);
    color: var(--text-primary);
}

.principle-card p {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: var(--space-sm);
}

.principle-list {
    list-style: none;
    padding: 0;
}

.principle-list li {
    position: relative;
    padding-left: 20px;
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.8;
}

.principle-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 10px;
    width: 6px;
    height: 6px;
    border-radius: 50%;
}

.advantage-list li::before { background: var(--accent-green); }
.disadvantage-list li::before { background: var(--accent-red); }

/* Characteristic Detail */
.characteristic-detail {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-xl);
}

.char-text ul {
    list-style: none;
    padding: 0;
    margin-top: var(--space-sm);
}

.char-text li {
    position: relative;
    padding-left: 20px;
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.8;
}

.char-text li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 10px;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent-cyan);
}

.formula {
    background: var(--bg-elevated);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
    padding: var(--space-md);
    margin: var(--space-md) 0;
    display: flex;
    align-items: center;
    gap: var(--space-md);
    flex-wrap: wrap;
}

.formula code {
    font-family: var(--font-mono);
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--accent-cyan);
}

.formula-note {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.char-comparison h4 {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: var(--space-md);
}

.comparison-table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    font-size: 0.82rem;
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
    overflow: hidden;
}

.comparison-table th {
    background: var(--bg-elevated);
    color: var(--text-muted);
    font-weight: 600;
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    padding: 8px 12px;
    text-align: center;
}

.comparison-table td {
    padding: 8px 12px;
    text-align: center;
    border-top: 1px solid var(--border-subtle);
    color: var(--text-secondary);
    font-family: var(--font-mono);
    font-size: 0.8rem;
}

.comparison-table td.highlight {
    color: var(--accent-cyan);
    font-weight: 700;
}

/* Applications Grid */
.applications-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-md);
    margin-top: var(--space-md);
}

.app-item {
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
    padding: var(--space-lg);
    transition: all var(--transition-base);
}

.app-item:hover {
    border-color: #2a3560;
    transform: translateY(-2px);
}

.app-badge {
    display: inline-block;
    padding: 3px 10px;
    border-radius: 6px;
    font-size: 0.65rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    background: var(--accent-blue);
    color: white;
    margin-bottom: var(--space-sm);
}

.app-badge.safety   { background: var(--accent-amber); color: #000; }
.app-badge.emergency { background: var(--accent-red); }
.app-badge.initial-flow { background: var(--accent-green); }

.app-item h4 {
    font-size: 0.9rem;
    font-weight: 700;
    margin-bottom: var(--space-sm);
    color: var(--text-primary);
}

.app-item p {
    font-size: 0.78rem;
    color: var(--text-muted);
    line-height: 1.6;
}

/* ── Construction Overlay ───────────────────────────────── */
.construction-overlay {
    position: fixed;
    inset: 0;
    z-index: 1000;
    background: rgba(0, 0, 0, 0.75);
    backdrop-filter: blur(8px);
    display: none;
    align-items: center;
    justify-content: center;
    animation: overlayIn 300ms ease;
}

.construction-overlay.active {
    display: flex;
}

@keyframes overlayIn {
    from { opacity: 0; }
    to   { opacity: 1; }
}

.construction-modal {
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-xl);
    width: 90%;
    max-width: 800px;
    max-height: 90vh;
    overflow: auto;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5);
    animation: modalIn 400ms cubic-bezier(0.22, 1, 0.36, 1);
}

@keyframes modalIn {
    from { opacity: 0; transform: scale(0.95) translateY(20px); }
    to   { opacity: 1; transform: scale(1) translateY(0); }
}

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-lg) var(--space-xl);
    border-bottom: 1px solid var(--border-subtle);
}

.modal-header h2 {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-primary);
}

.modal-close {
    width: 36px;
    height: 36px;
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);
    background: var(--bg-card);
    color: var(--text-muted);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.modal-close svg {
    width: 18px;
    height: 18px;
}

.modal-close:hover {
    background: var(--accent-red);
    border-color: var(--accent-red);
    color: white;
}

.modal-body {
    padding: var(--space-xl);
}

.construction-svg-container {
    width: 100%;
    display: flex;
    justify-content: center;
    margin-bottom: var(--space-lg);
}

.construction-svg-container svg {
    width: 100%;
    max-width: 700px;
    height: auto;
}

.construction-slider-section {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    padding: var(--space-md);
    background: var(--bg-card);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-subtle);
}

.construction-slider-section label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    white-space: nowrap;
}

.construction-slider-section input[type="range"] {
    flex: 1;
}

.construction-slider-section span {
    font-family: var(--font-mono);
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--accent-cyan);
    min-width: 40px;
    text-align: right;
}

/* ── Footer ─────────────────────────────────────────────── */
#lab-footer {
    text-align: center;
    padding: var(--space-xl);
    color: var(--text-muted);
    font-size: 0.75rem;
    border-top: 1px solid var(--border-subtle);
    margin-top: var(--space-xl);
}

/* ── SVG Component Labels ───────────────────────────────── */
.svg-label {
    font-family: 'Inter', sans-serif;
    font-size: 11px;
    font-weight: 600;
    fill: #94a3c0;
}

.svg-label-accent {
    font-family: 'Inter', sans-serif;
    font-size: 10px;
    font-weight: 700;
    fill: #60a5fa;
}

.svg-value {
    font-family: 'JetBrains Mono', monospace;
    font-size: 12px;
    font-weight: 700;
    fill: #22d3ee;
}

/* ── Water Particles ────────────────────────────────────── */
@keyframes flow-horizontal {
    from { transform: translateX(0); }
    to   { transform: translateX(40px); }
}

@keyframes flow-vertical {
    from { transform: translateY(0); }
    to   { transform: translateY(40px); }
}

/* ── Pump Animation ─────────────────────────────────────── */
@keyframes pump-rotate {
    from { transform: rotate(0deg); }
    to   { transform: rotate(360deg); }
}

.pump-impeller {
    transform-origin: 125px 310px;
    animation: pump-rotate 1s linear infinite;
    animation-play-state: paused;
}

.pump-impeller.spinning {
    animation-play-state: running;
}

/* ── Flow Meter ─────────────────────────────────────────── */
@keyframes meter-rotate {
    from { transform: rotate(0deg); }
    to   { transform: rotate(360deg); }
}

/* ── Responsive ─────────────────────────────────────────── */
@media (max-width: 1200px) {
    .top-section {
        grid-template-columns: 1fr;
    }
    .controls-column {
        display: grid;
        grid-template-columns: 1fr 1fr;
    }
    .applications-grid {
        grid-template-columns: 1fr 1fr;
    }
}

@media (max-width: 768px) {
    #lab-main {
        padding: var(--space-md);
    }
    .controls-column {
        grid-template-columns: 1fr;
    }
    .principle-grid {
        grid-template-columns: 1fr;
    }
    .characteristic-detail {
        grid-template-columns: 1fr;
    }
    .applications-grid {
        grid-template-columns: 1fr;
    }
    .header-content {
        padding: var(--space-sm) var(--space-md);
    }
    .header-text h1 {
        font-size: 0.9rem;
    }
    .tab-btn {
        padding: 10px 14px;
        font-size: 0.75rem;
    }
}

/* ── Scrollbar ──────────────────────────────────────────── */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--border-subtle);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}