/* ==========================================================================
   SNELL'S LAW OF REFRACTION — VIRTUAL PHYSICS LABORATORY CSS
   Design System: University Optics Bench Theme (Dark Slate, Cyan & Amber Accent)
   Branding: Virtual Instrumentation Labs
   ========================================================================== */

:root {
    --bg-primary: #0b0f19;
    --bg-secondary: #111827;
    --bg-card: #1e293b;
    --bg-card-hover: #334155;
    --border-color: #334155;
    --border-color-light: #475569;
    
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    
    --accent-blue: #3b82f6;
    --accent-blue-glow: rgba(59, 130, 246, 0.4);
    --accent-cyan: #06b6d4;
    --accent-amber: #f59e0b;
    --accent-amber-glow: rgba(245, 158, 11, 0.4);
    --accent-emerald: #10b981;
    --accent-rose: #ef4444;
    --laser-red: #ff3366;
    
    --font-sans: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', Consolas, monospace;
    
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --shadow-card: 0 10px 25px -5px rgba(0, 0, 0, 0.5), 0 8px 10px -6px rgba(0, 0, 0, 0.5);
    --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: var(--font-sans);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
    padding: 0;
    margin: 0;
}

/* App Shell Container */
.app-container {
    max-width: 1600px;
    margin: 0 auto;
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

/* Header Styling */
.app-header {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 16px 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow-card);
    flex-wrap: wrap;
    gap: 16px;
}

.header-left {
    display: flex;
    align-items: center;
    gap: 16px;
}

.logo-badge {
    width: 46px;
    height: 46px;
    border-radius: 12px;
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.2), rgba(6, 182, 212, 0.2));
    border: 1px solid var(--accent-cyan);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--accent-cyan);
    box-shadow: 0 0 15px rgba(6, 182, 212, 0.3);
}

.header-left h1 {
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

.header-left .subtitle {
    font-size: 0.82rem;
    color: var(--text-secondary);
}

.header-right {
    display: flex;
    align-items: center;
    gap: 16px;
}

.mode-selector {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 0.88rem;
    color: var(--text-secondary);
}

.mode-selector select {
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    padding: 8px 14px;
    border-radius: var(--radius-sm);
    font-family: var(--font-sans);
    font-size: 0.88rem;
    cursor: pointer;
    outline: none;
    transition: var(--transition);
}

.mode-selector select:focus {
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 2px var(--accent-blue-glow);
}

/* Button Styling */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    font-family: var(--font-sans);
    font-size: 0.88rem;
    font-weight: 600;
    cursor: pointer;
    border: 1px solid transparent;
    transition: var(--transition);
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent-blue), #2563eb);
    color: #fff;
}
.btn-primary:hover {
    background: linear-gradient(135deg, #2563eb, #1d4ed8);
    box-shadow: 0 0 15px var(--accent-blue-glow);
}

.btn-secondary {
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    border-color: var(--border-color);
}
.btn-secondary:hover {
    background-color: var(--border-color);
    color: #fff;
}

.btn-danger {
    background-color: rgba(239, 68, 68, 0.15);
    color: var(--accent-rose);
    border-color: rgba(239, 68, 68, 0.3);
}
.btn-danger:hover {
    background-color: var(--accent-rose);
    color: #fff;
}

.btn-outline {
    background: transparent;
    border-color: var(--border-color);
    color: var(--text-secondary);
}
.btn-outline:hover {
    border-color: var(--accent-cyan);
    color: var(--accent-cyan);
}

.btn-sm {
    padding: 6px 12px;
    font-size: 0.8rem;
}

.btn-chip {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    padding: 4px 10px;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}
.btn-chip:hover {
    border-color: var(--accent-blue);
    color: var(--accent-blue);
}

/* Card Styling */
.card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 20px;
    box-shadow: var(--shadow-card);
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
    padding-bottom: 10px;
}

.card-header h3, .card-header h2 {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--text-primary);
}

/* Badges */
.badge {
    font-size: 0.72rem;
    font-weight: 600;
    padding: 3px 8px;
    border-radius: 4px;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

.badge-primary { background: rgba(59, 130, 246, 0.2); color: var(--accent-blue); border: 1px solid rgba(59, 130, 246, 0.3); }
.badge-secondary { background: rgba(6, 182, 212, 0.2); color: var(--accent-cyan); border: 1px solid rgba(6, 182, 212, 0.3); }
.badge-success { background: rgba(16, 185, 129, 0.2); color: var(--accent-emerald); border: 1px solid rgba(16, 185, 129, 0.3); }
.badge-outline { border: 1px solid var(--border-color); color: var(--text-secondary); }
.info { background: rgba(148, 163, 184, 0.15); color: var(--text-secondary); }

/* Main Grid Layout */
.main-grid {
    display: grid;
    grid-template-columns: 360px 1fr;
    gap: 20px;
}

/* Sidebar Panel */
.sidebar-panel {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

/* Presets Grid */
.preset-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.preset-label {
    font-size: 0.8rem;
    color: var(--text-muted);
    font-weight: 500;
}

.preset-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
}

.preset-btn {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 8px 10px;
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    cursor: pointer;
    transition: var(--transition);
}

.preset-btn .preset-name {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-primary);
}

.preset-btn .preset-n {
    font-size: 0.75rem;
    color: var(--text-muted);
    font-family: var(--font-mono);
}

.preset-btn:hover {
    border-color: var(--accent-blue);
    background: rgba(59, 130, 246, 0.08);
}

.preset-btn.active {
    border-color: var(--accent-blue);
    background: rgba(59, 130, 246, 0.2);
    box-shadow: 0 0 10px rgba(59, 130, 246, 0.2);
}

.preset-btn.active .preset-name {
    color: var(--accent-blue);
}

.preset-btn.active .preset-n {
    color: var(--text-secondary);
}

/* Controls & Range Sliders */
.control-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.control-label-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.88rem;
}

.value-badge {
    font-family: var(--font-mono);
    font-weight: 700;
    color: var(--accent-cyan);
    background: rgba(6, 182, 212, 0.12);
    padding: 2px 8px;
    border-radius: 4px;
    border: 1px solid rgba(6, 182, 212, 0.2);
}

.value-badge.highlight {
    color: var(--accent-amber);
    background: rgba(245, 158, 11, 0.12);
    border-color: rgba(245, 158, 11, 0.2);
}

input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 6px;
    border-radius: 3px;
    background: var(--bg-secondary);
    outline: none;
    cursor: pointer;
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: var(--accent-blue);
    cursor: pointer;
    box-shadow: 0 0 10px var(--accent-blue-glow);
    border: 2px solid #fff;
    transition: transform 0.15s ease;
}

input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.2);
}

.slider-ticks {
    display: flex;
    justify-content: space-between;
    font-size: 0.72rem;
    color: var(--text-muted);
}

.quick-angle-buttons {
    display: flex;
    gap: 6px;
    justify-content: space-between;
    margin-top: 4px;
}

/* Medium Prediction Card */
.prediction-card {
    background: linear-gradient(135deg, rgba(30, 41, 59, 0.8), rgba(17, 24, 39, 0.9));
}

.index-compare-box {
    display: flex;
    align-items: center;
    justify-content: space-around;
    background: var(--bg-secondary);
    padding: 12px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
}

.compare-col {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.col-label {
    font-size: 0.75rem;
    color: var(--text-muted);
    font-family: var(--font-mono);
}

.col-val {
    font-size: 1.3rem;
    font-weight: 700;
    font-family: var(--font-mono);
    color: var(--accent-cyan);
}

.col-sub {
    font-size: 0.78rem;
    color: var(--text-secondary);
}

.compare-symbol {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--accent-amber);
    font-family: var(--font-mono);
}

.prediction-status {
    background: rgba(59, 130, 246, 0.1);
    border: 1px stroke rgba(59, 130, 246, 0.3);
    border-radius: var(--radius-sm);
    padding: 10px;
    font-size: 0.83rem;
    display: flex;
    align-items: center;
    gap: 8px;
    color: var(--text-primary);
}

.status-icon {
    font-size: 1.2rem;
    color: var(--accent-cyan);
}

/* Center Section: Optics Bench Hero Canvas */
.experiment-view {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.hero-canvas-card {
    padding: 16px;
    display: flex;
    flex-direction: column;
    gap: 12px;
    background: #0d1322;
    border-color: #1e293b;
}

.canvas-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.canvas-title {
    display: flex;
    align-items: center;
    gap: 10px;
    color: var(--accent-cyan);
}

.canvas-title h2 {
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--text-primary);
}

/* Canvas Container */
.canvas-container {
    position: relative;
    width: 100%;
    border-radius: var(--radius-md);
    overflow: hidden;
    background-color: #080c14;
    border: 1px solid #1e293b;
    box-shadow: inset 0 0 30px rgba(0, 0, 0, 0.8);
}

#opticsCanvas {
    display: block;
    width: 100%;
    height: auto;
}

/* Canvas Overlays */
.canvas-overlay-top-left,
.canvas-overlay-bottom-left,
.canvas-overlay-top-right {
    position: absolute;
    pointer-events: none;
    z-index: 10;
}

.canvas-overlay-top-left { top: 16px; left: 16px; }
.canvas-overlay-bottom-left { bottom: 16px; left: 16px; }
.canvas-overlay-top-right { top: 16px; right: 16px; }

.medium-tag {
    background: rgba(15, 23, 42, 0.75);
    backdrop-filter: blur(8px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    padding: 6px 12px;
    border-radius: var(--radius-sm);
    font-size: 0.8rem;
    display: flex;
    align-items: center;
    gap: 6px;
}

.tag-label { color: var(--text-muted); font-size: 0.7rem; font-weight: 600; }
.tag-value { font-weight: 700; color: #fff; }
.tag-n { font-family: var(--font-mono); color: var(--accent-cyan); font-weight: 600; }

.tir-alert-badge {
    background: rgba(239, 68, 68, 0.25);
    border: 1px solid var(--accent-rose);
    backdrop-filter: blur(8px);
    color: #ff8888;
    padding: 8px 14px;
    border-radius: var(--radius-sm);
    font-size: 0.82rem;
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: 8px;
    animation: pulseTIR 1.5s infinite alternate;
    box-shadow: 0 0 20px rgba(239, 68, 68, 0.4);
}

@keyframes pulseTIR {
    from { opacity: 0.8; transform: scale(0.98); }
    to { opacity: 1; transform: scale(1.02); }
}

/* Dashboard Row */
.dashboard-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
}

/* Metrics Grid */
.metrics-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
}

.metric-box {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    padding: 10px;
    border-radius: var(--radius-sm);
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.metric-label {
    font-size: 0.72rem;
    color: var(--text-muted);
}

.metric-value {
    font-size: 1.05rem;
    font-weight: 700;
    font-family: var(--font-mono);
}

.text-accent { color: var(--accent-blue); }
.text-success { color: var(--accent-emerald); }
.text-cyan { color: var(--accent-cyan); }
.text-amber { color: var(--accent-amber); }
.text-warning { color: #fbbf24; }
.text-danger { color: var(--accent-rose); }

/* Bending Direction Banner */
.direction-banner {
    background: rgba(59, 130, 246, 0.1);
    border: 1px solid rgba(59, 130, 246, 0.25);
    border-radius: var(--radius-sm);
    padding: 12px;
    display: flex;
    align-items: center;
    gap: 12px;
}

.dir-icon {
    width: 38px;
    height: 38px;
    border-radius: 50%;
    background: rgba(59, 130, 246, 0.2);
    color: var(--accent-cyan);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.3rem;
    font-weight: bold;
    flex-shrink: 0;
}

.dir-text {
    display: flex;
    flex-direction: column;
}

.dir-main {
    font-weight: 700;
    font-size: 0.95rem;
    color: var(--text-primary);
}

.dir-sub {
    font-size: 0.78rem;
    color: var(--text-secondary);
}

.angle-comparison-box {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 10px;
    background: var(--bg-secondary);
    padding: 10px 14px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
}

.comp-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.82rem;
}

.comp-label { color: var(--text-muted); }
.comp-val { font-family: var(--font-mono); font-weight: 700; }

/* Educational Light Speed Visualizer */
.speed-bars {
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.speed-row {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.speed-label {
    display: flex;
    justify-content: space-between;
    font-size: 0.8rem;
    font-weight: 600;
}

.speed-val {
    font-family: var(--font-mono);
    color: var(--accent-cyan);
}

.progress-track {
    width: 100%;
    height: 12px;
    background: var(--bg-secondary);
    border-radius: 6px;
    overflow: hidden;
    border: 1px solid var(--border-color);
}

.progress-bar {
    height: 100%;
    border-radius: 6px;
    transition: width 0.3s ease;
}

.bar-m1 { background: linear-gradient(90deg, #3b82f6, #06b6d4); }
.bar-m2 { background: linear-gradient(90deg, #f59e0b, #ef4444); }

/* Analysis Section (Graph & Verification) */
.analysis-section {
    margin-top: 10px;
}

.analysis-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
}

/* Graph Canvas */
.graph-container {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 10px;
    display: flex;
    justify-content: center;
}

#refractionGraph {
    max-width: 100%;
    height: auto;
    display: block;
}

.graph-legend {
    display: flex;
    justify-content: center;
    gap: 16px;
    font-size: 0.78rem;
    color: var(--text-secondary);
    margin-top: -6px;
}

.dot {
    display: inline-block;
    width: 10px;
    height: 10px;
    border-radius: 50%;
}

.dot-curve { background: var(--accent-blue); }
.dot-point { background: var(--accent-amber); }
.dot-critical { background: var(--accent-rose); }

/* Verification Panel */
.verification-content {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.verif-formula {
    display: flex;
    align-items: center;
    justify-content: space-around;
    background: var(--bg-secondary);
    padding: 16px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
}

.verif-side {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
}

.side-title { font-size: 0.7rem; color: var(--text-muted); font-weight: 700; letter-spacing: 0.05em; }
.side-eq { font-size: 0.85rem; font-family: var(--font-mono); color: var(--text-secondary); }
.side-calc { font-size: 0.8rem; font-family: var(--font-mono); color: var(--text-muted); }
.side-result { font-size: 1.25rem; font-family: var(--font-mono); font-weight: 700; color: var(--accent-cyan); }

.verif-equals {
    font-size: 1.6rem;
    font-weight: 800;
    color: var(--text-muted);
    font-family: var(--font-mono);
}

.verif-error-row {
    display: flex;
    justify-content: space-between;
    font-size: 0.88rem;
    background: rgba(255, 255, 255, 0.03);
    padding: 8px 12px;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
}

.verif-error-row strong { font-family: var(--font-mono); color: var(--text-primary); }

.verif-status-badge {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    padding: 12px;
    border-radius: var(--radius-sm);
    font-weight: 700;
    font-size: 0.95rem;
    letter-spacing: 0.02em;
    transition: var(--transition);
}

.verif-status-badge.verified {
    background: rgba(16, 185, 129, 0.15);
    border: 1px solid var(--accent-emerald);
    color: var(--accent-emerald);
}

.verif-status-badge.unverified {
    background: rgba(239, 68, 68, 0.15);
    border: 1px solid var(--accent-rose);
    color: var(--accent-rose);
}

/* Table Styling */
.table-section {
    margin-top: 10px;
}

.table-actions {
    display: flex;
    gap: 10px;
}

.table-wrapper {
    overflow-x: auto;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
}

table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.85rem;
    text-align: left;
}

thead {
    background: var(--bg-secondary);
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border-color);
}

th, td {
    padding: 10px 14px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

th { font-weight: 600; font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.04em; }

td { font-family: var(--font-mono); }

tbody tr:hover {
    background: rgba(255, 255, 255, 0.03);
}

.table-empty {
    text-align: center;
    padding: 30px;
    color: var(--text-muted);
    font-size: 0.88rem;
    background: var(--bg-secondary);
}

/* Guided Lab & Theory Styling */
.info-section {
    margin-top: 10px;
}

.info-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
}

.procedure-list {
    padding-left: 20px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    font-size: 0.88rem;
    color: var(--text-secondary);
}

.procedure-list li strong {
    color: var(--text-primary);
}

.theory-content {
    display: flex;
    flex-direction: column;
    gap: 12px;
    font-size: 0.88rem;
    color: var(--text-secondary);
}

.theory-content h4 {
    color: var(--accent-cyan);
    font-size: 0.95rem;
    font-weight: 600;
    margin-top: 4px;
}

.formula-box {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    padding: 10px;
    border-radius: var(--radius-sm);
    text-align: center;
    color: var(--accent-amber);
    font-size: 1.05rem;
}

/* Footer Styling */
.app-footer {
    text-align: center;
    padding: 20px 0;
    color: var(--text-muted);
    font-size: 0.8rem;
    border-top: 1px solid var(--border-color);
}

/* ==========================================================================
   RESPONSIVE DESIGN (TABLETS & MOBILE)
   ========================================================================== */

@media (max-width: 1100px) {
    .main-grid {
        grid-template-columns: 1fr;
    }
    
    .dashboard-row, .analysis-grid, .info-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 640px) {
    .app-container {
        padding: 10px;
    }
    
    .app-header {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .header-right {
        width: 100%;
        justify-content: space-between;
    }
    
    .metrics-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .table-actions {
        flex-direction: column;
        width: 100%;
    }
}