:root {
    /* Color Palette - Modern Light Theme */
    --bg-deep: #f0f2f5;
    --bg-card: #ffffff;
    --bg-sidebar: #ffffff;
    --bg-viewport: #ffffff;
    --accent-blue: #0066ff;
    --accent-light: rgba(0, 102, 255, 0.08);
    --text-main: #1a1d23;
    --text-muted: #64748b;
    --text-bright: #000000;
    --border-dim: #e2e8f0;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    
    /* Spacing & Sizing */
    --sidebar-width: 300px;
    --info-panel-width: 350px;
    --header-height: 64px;
    --radius: 10px;
    --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
    --font-mono: 'JetBrains Mono', 'Courier New', monospace;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.05);
}

* {
    box-sizing: border-box;
    -webkit-font-smoothing: antialiased;
}

body, html {
    margin: 0;
    padding: 0;
    height: 100%;
    background-color: var(--bg-deep);
    color: var(--text-main);
    font-family: var(--font-sans);
    overflow: hidden;
}

/* Layout Shell */
.app-shell {
    display: flex;
    width: 100vw;
    height: 100vh;
}

/* Sidebar Styling */
.sidebar {
    width: var(--sidebar-width);
    background-color: var(--bg-sidebar);
    border-right: 1px solid var(--border-dim);
    display: flex;
    flex-direction: column;
    z-index: 10;
    box-shadow: 2px 0 10px rgba(0,0,0,0.02);
}

.brand {
    padding: 24px;
    display: flex;
    align-items: center;
    gap: 12px;
}

.brand h1 {
    font-size: 1.1rem;
    font-weight: 800;
    letter-spacing: 1.5px;
    margin: 0;
    color: var(--text-bright);
}

.version {
    font-size: 0.65rem;
    font-weight: 600;
    color: var(--accent-blue);
    background: var(--accent-light);
    padding: 2px 8px;
    border-radius: 12px;
}

.sidebar-content {
    flex: 1;
    padding: 0 24px;
    overflow-y: auto;
}

.sidebar-footer {
    padding: 16px 24px;
    border-top: 1px solid var(--border-dim);
    font-size: 0.75rem;
    color: var(--text-muted);
}

/* UI Components */
.control-group {
    margin-bottom: 32px;
}

.group-label {
    display: block;
    font-size: 0.7rem;
    font-weight: 700;
    text-transform: uppercase;
    color: var(--text-muted);
    letter-spacing: 1px;
    margin-bottom: 12px;
}

textarea, input[type="number"], input[type="text"] {
    width: 100%;
    background: #f8fafc;
    border: 1px solid var(--border-dim);
    border-radius: var(--radius);
    color: var(--text-main);
    padding: 12px;
    font-family: var(--font-sans);
    font-size: 0.9rem;
    transition: all 0.2s;
}

textarea:focus, input:focus {
    outline: none;
    border-color: var(--accent-blue);
    background: #fff;
    box-shadow: 0 0 0 3px var(--accent-light);
}

.param-grid {
    display: flex;
    gap: 12px;
    margin-top: 12px;
    align-items: flex-end;
}

.param-item {
    flex: 1;
}

.param-item label {
    font-size: 0.75rem;
    font-weight: 500;
    display: block;
    margin-bottom: 4px;
    color: var(--text-muted);
}

.checkbox-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding-bottom: 12px;
}

.checkbox-item label {
    font-size: 0.85rem;
    font-weight: 500;
    margin: 0;
}

.btn-primary {
    width: 100%;
    background: var(--accent-blue);
    color: #ffffff;
    border: none;
    border-radius: var(--radius);
    padding: 14px;
    font-weight: 600;
    cursor: pointer;
    margin-top: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    transition: all 0.2s;
    box-shadow: 0 4px 12px rgba(0, 102, 255, 0.2);
}

.btn-primary:hover {
    transform: translateY(-1px);
    box-shadow: 0 6px 15px rgba(0, 102, 255, 0.25);
}

.btn-primary:active {
    transform: translateY(0);
}

.disabled-control {
    opacity: 0.5;
    pointer-events: none;
    position: relative;
}

.disabled-control::after {
    content: " (Auto)";
    font-size: 0.65rem;
    color: var(--accent-blue);
    font-weight: 600;
}

/* Playback Controls */
.playback-controls {
    display: flex;
    justify-content: space-between;
    gap: 8px;
    margin-bottom: 16px;
}

.playback-controls button {
    flex: 1;
    background: #f1f5f9;
    border: 1px solid var(--border-dim);
    color: var(--text-main);
    padding: 10px 0;
    border-radius: var(--radius);
    cursor: pointer;
    font-size: 1rem;
    line-height: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
}

.playback-controls button svg {
    width: 1.2rem;
    height: 1.2rem;
    display: block;
}

#playBtn {
    gap: 6px;
    flex: 1.8;
}

#play-icon-container {
    display: flex;
    align-items: center;
}

.playback-controls button.icon-btn {
    padding: 10px 0;
}

.playback-controls button:hover {
    background: #e2e8f0;
}

.playback-controls .btn-highlight {
    background: var(--accent-blue);
    color: #ffffff;
    border: none;
    font-weight: 600;
    box-shadow: 0 4px 10px rgba(0, 102, 255, 0.15);
}

.speed-control label {
    font-size: 0.75rem;
    font-weight: 500;
    margin-bottom: 12px;
    display: block;
    color: var(--text-muted);
}

.speed-input-wrapper {
    display: flex;
    align-items: center;
    gap: 12px;
}

input[type="range"] {
    flex: 1;
    accent-color: var(--accent-blue);
}

.speed-input-wrapper input[type="number"] {
    width: 65px;
    padding: 8px;
}

/* Viewport Shell */
.viewport {
    flex: 1;
    display: flex;
    flex-direction: column;
    background-color: var(--bg-viewport);
    position: relative;
    min-height: 0;
}

.viewport-header {
    height: var(--header-height);
    display: flex;
    align-items: center;
    padding: 0 24px;
    border-bottom: 1px solid var(--border-dim);
    background: #ffffff;
}

.status-badge {
    background: #f1f5f9;
    border: 1px solid var(--border-dim);
    color: var(--text-muted);
    padding: 8px 16px;
    border-radius: 30px;
    font-size: 0.75rem;
    font-weight: 600;
    font-family: var(--font-mono);
}

.svg-container {
    flex: 1;
    position: relative;
    overflow: hidden;
    background-color: #ffffff;
    min-height: 0;
}

.svg-container svg {
    display: block;
    width: 100%;
    height: 100%;
}

/* Info Panel Styling */
.info-panel {
    width: var(--info-panel-width);
    background-color: var(--bg-sidebar);
    border-left: 1px solid var(--border-dim);
    display: flex;
    flex-direction: column;
    box-shadow: -2px 0 10px rgba(0,0,0,0.02);
}

.panel-header {
    padding: 20px 24px;
    border-bottom: 1px solid var(--border-dim);
    height: var(--header-height);
    display: flex;
    align-items: center;
}

.panel-header h2 {
    font-size: 0.9rem;
    margin: 0;
    font-weight: 700;
    color: var(--text-bright);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.panel-content {
    padding: 24px;
    overflow-y: auto;
}

.data-card {
    background: #ffffff;
    border: 1px solid var(--border-dim);
    border-radius: var(--radius);
    padding: 20px;
    margin-bottom: 24px;
    box-shadow: var(--shadow-sm);
}

.stimulus-display {
    font-size: 2.8rem;
    font-weight: 800;
    color: var(--accent-blue);
    text-align: center;
    margin: 12px 0;
    font-family: var(--font-mono);
}

.mono-display {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    background: #f8fafc;
    padding: 16px;
    border-radius: var(--radius);
    min-height: 100px;
    max-height: 250px;
    overflow-y: auto;
    border: 1px solid var(--border-dim);
    color: var(--text-main);
    line-height: 1.5;
}

/* Progress Bar */
.progress-card {
    background: #ffffff;
    border: 1px solid var(--accent-blue);
    padding: 20px;
    border-radius: var(--radius);
    margin-top: 24px;
    box-shadow: 0 10px 15px -3px rgba(0, 102, 255, 0.1);
}

.progress-header {
    font-size: 0.75rem;
    font-weight: 600;
    margin-bottom: 10px;
    color: var(--accent-blue);
}

.progress-track {
    height: 10px;
    background: #f1f5f9;
    border-radius: 5px;
    overflow: hidden;
}

#progressBar {
    height: 100%;
    background: var(--accent-blue);
    width: 0%;
    transition: width 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Legend Specifics */
.legend-card {
    padding: 12px;
}

.legend-svg text {
    fill: var(--text-muted) !important;
    font-weight: 500;
}

.legend-svg path {
    stroke: #e2e8f0 !important;
}

/* Simulation Adjustments */
.node-label {
    font-size: 12px;
}