/* ==========================================================================
   Damped Harmonic Oscillation Lab - Stylesheet
   Modern Scientific Dark UI with Glassmorphism & High-Contrast Visualizations
   ========================================================================== */

:root {
  /* Color Palette */
  --bg-primary: #0a0e17;
  --bg-surface: #111827;
  --bg-card: rgba(22, 31, 48, 0.75);
  --bg-card-hover: rgba(27, 39, 61, 0.85);
  --border-subtle: #1e293b;
  --border-card: #28374f;
  --border-highlight: #3b82f6;

  /* Typography Colors */
  --text-main: #f1f5f9;
  --text-muted: #94a3b8;
  --text-dim: #64748b;

  /* Physics Visualization Accent Colors */
  --color-displacement: #38bdf8;       /* Electric Sky Blue */
  --color-envelope: #c084fc;           /* Soft Violet / Purple */
  --color-restoring: #10b981;          /* Emerald Green */
  --color-damping: #f59e0b;            /* Vivid Amber */
  --color-velocity: #06b6d4;           /* Vibrant Cyan */
  --color-net-force: #ef4444;          /* Crimson / Rose */

  /* Regime Specific Colors */
  --color-under: #38bdf8;
  --color-critical: #f59e0b;
  --color-over: #ec4899;

  /* UI Glows & Shadows */
  --glow-under: 0 0 16px rgba(56, 189, 248, 0.25);
  --glow-critical: 0 0 16px rgba(245, 158, 11, 0.25);
  --glow-over: 0 0 16px rgba(236, 72, 153, 0.25);
  --card-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.5), 0 8px 10px -6px rgba(0, 0, 0, 0.4);

  /* Dimensions & Transitions */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-main);
  line-height: 1.5;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  background-image: 
    radial-gradient(circle at 15% 10%, rgba(56, 189, 248, 0.04) 0%, transparent 40%),
    radial-gradient(circle at 85% 85%, rgba(245, 158, 11, 0.04) 0%, transparent 40%);
  background-attachment: fixed;
  overflow-x: hidden;
}

.app-container {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  max-width: 1720px;
  width: 100%;
  margin: 0 auto;
  padding: 16px 24px 20px 24px;
  gap: 16px;
}

/* ==========================================================================
   Header & Mode Selector
   ========================================================================== */
.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
  padding: 12px 20px;
  background: var(--bg-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-lg);
  box-shadow: var(--card-shadow);
}

.header-brand {
  display: flex;
  align-items: center;
  gap: 14px;
}

.brand-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  flex-shrink: 0;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, rgba(56, 189, 248, 0.2), rgba(16, 185, 129, 0.2));
  color: var(--color-displacement);
  border: 1px solid rgba(56, 189, 248, 0.3);
  box-shadow: var(--glow-under);
}

.app-header h1 {
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: #fff;
}

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

/* Mode Switcher Buttons */
.mode-selector {
  display: flex;
  background: rgba(10, 14, 23, 0.8);
  padding: 4px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-card);
  gap: 4px;
}

.mode-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  background: transparent;
  color: var(--text-muted);
  border: 1px solid transparent;
  border-radius: var(--radius-md);
  font-size: 0.86rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.mode-btn:hover {
  color: var(--text-main);
  background: rgba(255, 255, 255, 0.05);
}

.mode-indicator {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--text-dim);
  transition: var(--transition);
}

.mode-indicator.under { background: var(--color-under); }
.mode-indicator.critical { background: var(--color-critical); }
.mode-indicator.over { background: var(--color-over); }

.mode-cond {
  font-size: 0.75rem;
  padding: 1px 6px;
  border-radius: 4px;
  background: rgba(255, 255, 255, 0.08);
  color: var(--text-muted);
  font-family: monospace;
}

.mode-btn.active {
  background: var(--bg-card-hover);
  color: #fff;
  border-color: var(--border-card);
}

.mode-btn.active[data-mode="underdamped"] {
  border-color: rgba(56, 189, 248, 0.4);
  box-shadow: 0 0 12px rgba(56, 189, 248, 0.2);
}

.mode-btn.active[data-mode="critical"] {
  border-color: rgba(245, 158, 11, 0.4);
  box-shadow: 0 0 12px rgba(245, 158, 11, 0.2);
}

.mode-btn.active[data-mode="overdamped"] {
  border-color: rgba(236, 72, 153, 0.4);
  box-shadow: 0 0 12px rgba(236, 72, 153, 0.2);
}

/* ==========================================================================
   Main Grid Layout
   ========================================================================== */
.main-grid {
  display: grid;
  grid-template-columns: 360px minmax(0, 1fr);
  gap: 16px;
  flex: 1;
}

/* ==========================================================================
   Left Sidebar: Controls & Inputs
   ========================================================================== */
.sidebar-panel {
  background: var(--bg-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-lg);
  padding: 18px;
  box-shadow: var(--card-shadow);
  display: flex;
  flex-direction: column;
  gap: 16px;
  max-height: calc(100vh - 120px);
  overflow-y: auto;
}

.sidebar-panel::-webkit-scrollbar {
  width: 6px;
}
.sidebar-panel::-webkit-scrollbar-thumb {
  background: var(--border-card);
  border-radius: 4px;
}

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

.panel-header h2 {
  font-size: 1.05rem;
  font-weight: 700;
  color: #fff;
}

.icon-action-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-card);
  color: var(--text-muted);
  border-radius: var(--radius-sm);
  padding: 4px 10px;
  font-size: 0.78rem;
  cursor: pointer;
  transition: var(--transition);
}

.icon-action-btn:hover {
  background: rgba(255, 255, 255, 0.1);
  color: #fff;
  border-color: var(--text-muted);
}

.control-groups-container {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.control-section {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.section-title {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.badge {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  padding: 3px 8px;
  border-radius: var(--radius-sm);
}

.badge.blue {
  background: rgba(56, 189, 248, 0.15);
  color: var(--color-displacement);
  border: 1px solid rgba(56, 189, 248, 0.3);
}

.badge.purple {
  background: rgba(192, 132, 252, 0.15);
  color: var(--color-envelope);
  border: 1px solid rgba(192, 132, 252, 0.3);
}

/* Control Row & Slider Styles */
.control-row {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.control-row.compact {
  gap: 4px;
}

.mt-2 {
  margin-top: 8px;
}

.label-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.85rem;
}

.label-row label {
  color: var(--text-main);
  display: flex;
  flex-direction: column;
}

.formula-hint {
  font-size: 0.72rem;
  color: var(--text-dim);
  font-family: monospace;
}

.input-with-unit {
  display: flex;
  align-items: center;
  background: rgba(10, 14, 23, 0.7);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-sm);
  padding: 2px 6px;
  transition: var(--transition);
}

.input-with-unit:focus-within {
  border-color: var(--border-highlight);
  box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.2);
}

.input-with-unit input[type="number"] {
  width: 58px;
  background: transparent;
  border: none;
  color: #fff;
  font-size: 0.85rem;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-variant-numeric: tabular-nums;
  text-align: right;
  outline: none;
}

.input-with-unit input[type="number"]::-webkit-inner-spin-button,
.input-with-unit input[type="number"]::-webkit-outer-spin-button {
  opacity: 0.4;
}

.input-with-unit .unit {
  font-size: 0.75rem;
  color: var(--text-dim);
  margin-left: 4px;
}

/* Custom Styled Range Sliders */
.styled-slider {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 6px;
  border-radius: 3px;
  background: #1e293b;
  outline: none;
  cursor: pointer;
  transition: background 0.2s;
}

.styled-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: #fff;
  cursor: pointer;
  box-shadow: 0 0 8px rgba(0, 0, 0, 0.6);
  border: 2px solid var(--color-displacement);
  transition: transform 0.15s ease, background-color 0.15s ease;
}

.styled-slider::-webkit-slider-thumb:hover {
  transform: scale(1.2);
  background: var(--color-displacement);
}

.styled-slider.beta-slider::-webkit-slider-thumb,
.styled-slider.gamma-slider::-webkit-slider-thumb {
  border-color: var(--color-damping);
}
.styled-slider.beta-slider::-webkit-slider-thumb:hover,
.styled-slider.gamma-slider::-webkit-slider-thumb:hover {
  background: var(--color-damping);
}

.styled-slider.omega-slider::-webkit-slider-thumb {
  border-color: var(--color-restoring);
}
.styled-slider.omega-slider::-webkit-slider-thumb:hover {
  background: var(--color-restoring);
}

/* Action Button */
.action-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 8px 14px;
  border-radius: var(--radius-md);
  font-size: 0.82rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: var(--transition);
}

.action-btn.secondary {
  background: rgba(245, 158, 11, 0.12);
  color: #fbbf24;
  border: 1px solid rgba(245, 158, 11, 0.3);
}

.action-btn.secondary:hover {
  background: rgba(245, 158, 11, 0.22);
  border-color: rgba(245, 158, 11, 0.5);
  box-shadow: 0 0 10px rgba(245, 158, 11, 0.2);
}

/* Accordion for Physical components (m, b, k) */
.control-accordion {
  border: 1px solid var(--border-card);
  border-radius: var(--radius-md);
  background: rgba(10, 14, 23, 0.4);
  overflow: hidden;
}

.accordion-header {
  padding: 10px 14px;
  font-size: 0.84rem;
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  list-style: none;
  user-select: none;
  transition: var(--transition);
}

.accordion-header:hover {
  color: #fff;
  background: rgba(255, 255, 255, 0.03);
}

.accordion-arrow {
  font-size: 1.1rem;
  transition: transform 0.2s ease;
}

.control-accordion[open] .accordion-arrow {
  transform: rotate(90deg);
}

.accordion-body {
  padding: 12px 14px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  border-top: 1px solid var(--border-subtle);
}

/* Toggle Checkboxes */
.toggle-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.toggle-item {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.82rem;
  cursor: pointer;
  user-select: none;
  color: var(--text-muted);
  padding: 4px 6px;
  border-radius: var(--radius-sm);
  transition: var(--transition);
}

.toggle-item:hover {
  color: #fff;
  background: rgba(255, 255, 255, 0.03);
}

.toggle-item.highlight-toggle {
  background: rgba(56, 189, 248, 0.06);
  border: 1px dashed rgba(56, 189, 248, 0.3);
  padding: 6px 8px;
}

.toggle-item input[type="checkbox"] {
  display: none;
}

.custom-check {
  width: 16px;
  height: 16px;
  border: 1.5px solid var(--border-card);
  border-radius: 4px;
  background: rgba(10, 14, 23, 0.6);
  position: relative;
  transition: var(--transition);
  flex-shrink: 0;
}

.toggle-item input[type="checkbox"]:checked + .custom-check {
  background: var(--border-highlight);
  border-color: var(--border-highlight);
}

.toggle-item input[type="checkbox"]:checked + .custom-check::after {
  content: "";
  position: absolute;
  left: 4.5px;
  top: 1.5px;
  width: 4px;
  height: 8px;
  border: solid #fff;
  border-width: 0 2px 2px 0;
  transform: rotate(45deg);
}

.toggle-label {
  display: flex;
  align-items: center;
  gap: 6px;
}

.color-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
}

.envelope-dot { background: var(--color-envelope); }
.restoring-dot { background: var(--color-restoring); }
.damping-dot { background: var(--color-damping); }
.velocity-dot { background: var(--color-velocity); }
.compare-dot { background: linear-gradient(135deg, var(--color-under), var(--color-over)); }

/* ==========================================================================
   Visualization Column (Center & Right)
   ========================================================================== */
.visualization-column {
  display: flex;
  flex-direction: column;
  gap: 16px;
  min-width: 0;
}

/* Formula Banner */
.formula-banner {
  display: grid;
  grid-template-columns: 1.3fr 1.5fr auto;
  gap: 14px;
  background: var(--bg-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-lg);
  padding: 14px 20px;
  box-shadow: var(--card-shadow);
  align-items: center;
}

.formula-block {
  display: flex;
  flex-direction: column;
  gap: 4px;
  min-width: 0;
}

.formula-tag {
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-dim);
  font-weight: 700;
}

.math-expr {
  font-family: "Cambria Math", "Latin Modern Math", KaTeX_Math, "Times New Roman", serif;
  font-size: 1.08rem;
  letter-spacing: 0.02em;
  color: #fff;
  overflow-x: auto;
  scrollbar-width: thin;
  -webkit-overflow-scrolling: touch;
}

.solution-expr {
  color: #7dd3fc;
}

.highlight-beta,
.highlight-gamma {
  color: #f59e0b;
}

.highlight-omega0 {
  color: #10b981;
}

.formula-subtext {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

.formula-status-pill {
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 8px 16px;
  border-radius: var(--radius-md);
  background: rgba(56, 189, 248, 0.1);
  border: 1px solid rgba(56, 189, 248, 0.3);
  min-width: 170px;
  transition: var(--transition);
}

.formula-status-pill .status-dot {
  display: none;
}

#regimeTitle {
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--color-under);
}

#regimeSub {
  font-size: 0.74rem;
  color: var(--text-muted);
  font-family: monospace;
}

.formula-status-pill.under {
  background: rgba(56, 189, 248, 0.1);
  border-color: rgba(56, 189, 248, 0.3);
}
.formula-status-pill.under #regimeTitle { color: var(--color-under); }

.formula-status-pill.critical {
  background: rgba(245, 158, 11, 0.1);
  border-color: rgba(245, 158, 11, 0.3);
}
.formula-status-pill.critical #regimeTitle { color: var(--color-critical); }

.formula-status-pill.over {
  background: rgba(236, 72, 153, 0.1);
  border-color: rgba(236, 72, 153, 0.3);
}
.formula-status-pill.over #regimeTitle { color: var(--color-over); }

/* ==========================================================================
   Main Chart Card
   ========================================================================== */
.chart-card {
  background: var(--bg-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-lg);
  padding: 16px 20px;
  box-shadow: var(--card-shadow);
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.chart-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
}

.chart-title-group h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: #fff;
}

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

.view-mode-tabs {
  display: flex;
  background: rgba(10, 14, 23, 0.6);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-md);
  padding: 3px;
  gap: 4px;
}

.view-tab-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-size: 0.78rem;
  font-weight: 600;
  padding: 5px 12px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
}

.view-tab-btn:hover {
  color: #fff;
}

.view-tab-btn.active {
  background: var(--border-card);
  color: #fff;
}

.chart-actions {
  display: flex;
  gap: 8px;
}

.toolbar-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 10px;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-sm);
  color: var(--text-muted);
  font-size: 0.76rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.toolbar-btn:hover {
  background: rgba(255, 255, 255, 0.1);
  color: #fff;
  border-color: var(--text-muted);
}

/* Canvas Wrapper & Tooltip */
.canvas-wrapper {
  position: relative;
  width: 100%;
  height: 380px;
  background: #090d16;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  overflow: hidden;
}

#graphCanvas {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: block;
}

.graph-tooltip {
  position: absolute;
  display: none;
  pointer-events: none;
  background: rgba(17, 24, 39, 0.95);
  backdrop-filter: blur(8px);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-sm);
  padding: 8px 12px;
  font-size: 0.75rem;
  color: #fff;
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.6);
  z-index: 10;
  transform: translate(12px, -50%);
  min-width: 140px;
  max-width: calc(100% - 24px);
  transition: transform 0.1s ease;
}

.tooltip-header {
  font-weight: 700;
  color: #fff;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
  padding-bottom: 4px;
  margin-bottom: 6px;
  font-family: monospace;
}

.tooltip-grid {
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.tt-item {
  display: flex;
  justify-content: space-between;
  gap: 8px;
  font-family: monospace;
}

.tt-x .tt-val { color: var(--color-displacement); font-weight: 600; }
.tt-v .tt-val { color: var(--color-velocity); font-weight: 600; }
.tt-fk .tt-val { color: var(--color-restoring); font-weight: 600; }
.tt-fb .tt-val { color: var(--color-damping); font-weight: 600; }

/* Chart Legend */
.chart-legend {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
  font-size: 0.78rem;
  color: var(--text-muted);
  padding-top: 4px;
}

.legend-item {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.legend-line {
  width: 20px;
  height: 3px;
  border-radius: 2px;
  display: inline-block;
}

.line-x { background: var(--color-displacement); }
.line-env { background: var(--color-envelope); border-top: 1px dashed var(--color-envelope); height: 2px; }
.line-fk { background: var(--color-restoring); }
.line-fb { background: var(--color-damping); }
.line-v { background: var(--color-velocity); }

/* ==========================================================================
   Simulation & Metrics Grid (Bottom Row)
   ========================================================================== */
.simulation-metrics-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}

/* Physical Simulation Card */
.simulation-card {
  background: var(--bg-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-lg);
  padding: 16px 20px;
  box-shadow: var(--card-shadow);
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.sim-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
}

.sim-title h3 {
  font-size: 0.98rem;
  font-weight: 700;
  color: #fff;
}

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

.sim-controls {
  display: flex;
  align-items: center;
  gap: 8px;
}

.ctrl-icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-card);
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-main);
  cursor: pointer;
  transition: var(--transition);
}

.ctrl-icon-btn:hover {
  background: rgba(255, 255, 255, 0.12);
  border-color: var(--text-muted);
}

.ctrl-icon-btn.primary {
  background: #2563eb;
  border-color: #3b82f6;
  color: #fff;
}

.ctrl-icon-btn.primary:hover {
  background: #1d4ed8;
  box-shadow: 0 0 10px rgba(59, 130, 246, 0.4);
}

.speed-selector {
  display: flex;
  background: rgba(10, 14, 23, 0.6);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-sm);
  padding: 2px;
}

.speed-btn {
  background: transparent;
  border: none;
  color: var(--text-dim);
  font-size: 0.72rem;
  font-weight: 600;
  padding: 3px 6px;
  border-radius: 3px;
  cursor: pointer;
  transition: var(--transition);
}

.speed-btn:hover {
  color: var(--text-main);
}

.speed-btn.active {
  background: var(--border-card);
  color: #fff;
}

/* Simulation Canvas Container */
.sim-canvas-container {
  width: 100%;
  height: 160px;
  background: #090d16;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  overflow: hidden;
  position: relative;
}

#simCanvas {
  width: 100%;
  height: 100%;
  display: block;
}

/* Scrubber Bar */
.scrubber-bar {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 0.78rem;
  color: var(--text-muted);
}

.scrub-label strong {
  color: #fff;
  font-family: monospace;
}

.scrub-total {
  font-family: monospace;
}

.time-slider {
  flex: 1;
  -webkit-appearance: none;
  appearance: none;
  height: 5px;
  background: #1e293b;
  border-radius: 3px;
  outline: none;
  cursor: pointer;
}

.time-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--color-displacement);
  cursor: pointer;
  box-shadow: 0 0 6px var(--color-displacement);
}

/* Vector Legend */
.vector-legend {
  display: flex;
  gap: 12px;
  font-size: 0.75rem;
  flex-wrap: wrap;
}

.vector-tag {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-weight: 600;
}

.tag-arrow { font-size: 0.9rem; }
.tag-k { color: var(--color-restoring); }
.tag-b { color: var(--color-damping); }
.tag-v { color: var(--color-velocity); }

/* ==========================================================================
   Metrics Card
   ========================================================================== */
.metrics-card {
  background: var(--bg-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-lg);
  padding: 16px 20px;
  box-shadow: var(--card-shadow);
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.metrics-header h3 {
  font-size: 0.98rem;
  font-weight: 700;
  color: #fff;
}

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

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

.metric-box {
  background: rgba(10, 14, 23, 0.6);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 10px;
  display: flex;
  flex-direction: column;
  gap: 2px;
  transition: var(--transition);
}

.metric-box:hover {
  border-color: var(--border-card);
  background: rgba(10, 14, 23, 0.8);
}

.metric-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.metric-symbol {
  font-family: serif;
  font-weight: 700;
  font-size: 0.9rem;
  color: #7dd3fc;
}

.metric-name {
  font-size: 0.68rem;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  font-weight: 600;
}

.metric-value {
  font-size: 1.15rem;
  font-weight: 700;
  color: #fff;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-variant-numeric: tabular-nums;
}

.metric-value small {
  font-size: 0.72rem;
  font-weight: normal;
  color: var(--text-dim);
}

.metric-desc {
  font-size: 0.68rem;
  color: var(--text-muted);
  font-family: monospace;
}

.regime-explanation-box {
  background: rgba(255, 255, 255, 0.02);
  border-left: 3px solid var(--color-under);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  padding: 10px 14px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  transition: border-color 0.2s;
}

.regime-explanation-box h4 {
  font-size: 0.85rem;
  font-weight: 700;
  color: #fff;
}

.regime-explanation-box p {
  font-size: 0.8rem;
  color: var(--text-muted);
  line-height: 1.45;
}

/* ==========================================================================
   Footer
   ========================================================================== */
.app-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
  padding: 10px 16px;
  font-size: 0.75rem;
  color: var(--text-dim);
  border-top: 1px solid var(--border-subtle);
}

.app-footer code {
  background: rgba(255, 255, 255, 0.06);
  padding: 2px 6px;
  border-radius: 4px;
  color: var(--text-muted);
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

/* ==========================================================================
   Responsive Architecture: Devices, Laptops, Tablets & Phones
   Utilizing CSS '@media screen and (...)' with conditions for all viewports
   ========================================================================== */

/* --------------------------------------------------------------------------
   1. Ultra-Wide Screens & Large Desktop Displays (min-width: 1440px)
   -------------------------------------------------------------------------- */
@media screen and (min-width: 1440px) {
  .app-container {
    max-width: 1800px;
    padding: 20px 32px;
    gap: 18px;
  }

  .main-grid {
    grid-template-columns: 380px minmax(0, 1fr);
    gap: 20px;
  }

  .canvas-wrapper {
    height: 420px;
  }

  .sim-canvas-container {
    height: 180px;
  }

  .formula-banner {
    grid-template-columns: 1.3fr 1.6fr auto;
    padding: 16px 24px;
    gap: 20px;
  }

  .metric-value {
    font-size: 1.25rem;
  }
}

/* --------------------------------------------------------------------------
   2. Standard Laptops & Notebooks (min-width: 1025px) and (max-width: 1439px)
   -------------------------------------------------------------------------- */
@media screen and (min-width: 1025px) and (max-width: 1439px) {
  .app-container {
    padding: 14px 20px;
    gap: 14px;
  }

  .main-grid {
    grid-template-columns: 330px minmax(0, 1fr);
    gap: 14px;
  }

  .sidebar-panel {
    padding: 16px;
    max-height: calc(100vh - 110px);
  }

  .canvas-wrapper {
    height: 360px;
  }

  .sim-canvas-container {
    height: 155px;
  }

  .formula-banner {
    grid-template-columns: 1.2fr 1.4fr auto;
    gap: 12px;
    padding: 12px 18px;
  }

  .math-expr {
    font-size: 1rem;
  }

  .simulation-metrics-grid {
    grid-template-columns: 1fr 1fr;
    gap: 14px;
  }

  .metrics-dashboard {
    grid-template-columns: repeat(3, 1fr);
    gap: 8px;
  }

  .metric-box {
    padding: 8px 10px;
  }

  .metric-value {
    font-size: 1.08rem;
  }
}

/* --------------------------------------------------------------------------
   3. Small Laptops, Netbooks & Tablets Landscape (min-width: 769px) and (max-width: 1024px)
   -------------------------------------------------------------------------- */
@media screen and (min-width: 769px) and (max-width: 1024px) {
  .app-container {
    padding: 12px 16px;
    gap: 12px;
  }

  .app-header {
    padding: 10px 16px;
  }

  .app-header h1 {
    font-size: 1.15rem;
  }

  .mode-btn {
    padding: 6px 10px;
    font-size: 0.78rem;
  }

  .main-grid {
    grid-template-columns: 1fr;
    gap: 14px;
  }

  .sidebar-panel {
    max-height: none;
    overflow-y: visible;
  }

  .formula-banner {
    grid-template-columns: 1fr 1fr;
    gap: 12px;
  }

  .formula-status-pill {
    grid-column: 1 / -1;
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
    padding: 10px 16px;
  }

  .canvas-wrapper {
    height: 340px;
  }

  .simulation-metrics-grid {
    grid-template-columns: 1fr;
    gap: 14px;
  }

  .sim-canvas-container {
    height: 160px;
  }

  .metrics-dashboard {
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
  }
}

/* --------------------------------------------------------------------------
   4. Tablets (Portrait) & Large Mobile Phones (max-width: 768px)
   -------------------------------------------------------------------------- */
@media screen and (max-width: 768px) {
  .app-container {
    padding: 10px 12px;
    gap: 12px;
  }

  .app-header {
    flex-direction: column;
    align-items: stretch;
    gap: 12px;
    padding: 12px 14px;
  }

  .header-brand {
    justify-content: flex-start;
  }

  .mode-selector {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    width: 100%;
    gap: 3px;
  }

  .mode-btn {
    flex-direction: column;
    gap: 3px;
    padding: 8px 4px;
    text-align: center;
    justify-content: center;
    font-size: 0.76rem;
  }

  .mode-cond {
    font-size: 0.68rem;
    padding: 1px 4px;
  }

  .main-grid {
    grid-template-columns: 1fr;
    gap: 12px;
  }

  .sidebar-panel {
    max-height: none;
    overflow-y: visible;
    padding: 16px 14px;
  }

  .formula-banner {
    grid-template-columns: 1fr;
    gap: 12px;
    padding: 12px 14px;
  }

  .formula-status-pill {
    width: 100%;
    text-align: center;
    align-items: center;
  }

  .chart-card {
    padding: 14px 14px;
  }

  .chart-toolbar {
    flex-direction: column;
    align-items: stretch;
    gap: 10px;
  }

  .chart-title-group {
    width: 100%;
  }

  .view-mode-tabs {
    display: flex;
    width: 100%;
  }

  .view-tab-btn {
    flex: 1;
    text-align: center;
    padding: 7px 8px;
    font-size: 0.74rem;
  }

  .chart-actions {
    display: flex;
    width: 100%;
    gap: 8px;
  }

  .toolbar-btn {
    flex: 1;
    justify-content: center;
    padding: 7px 8px;
  }

  .canvas-wrapper {
    height: 300px;
  }

  .chart-legend {
    gap: 10px 14px;
    font-size: 0.74rem;
  }

  .simulation-metrics-grid {
    grid-template-columns: 1fr;
    gap: 12px;
  }

  .simulation-card {
    padding: 14px 14px;
  }

  .sim-canvas-container {
    height: 150px;
  }

  .metrics-card {
    padding: 14px 14px;
  }

  .metrics-dashboard {
    grid-template-columns: repeat(3, 1fr);
    gap: 8px;
  }

  .app-footer {
    flex-direction: column;
    text-align: center;
    gap: 6px;
    font-size: 0.72rem;
  }
}

/* --------------------------------------------------------------------------
   5. Mobile Phones (max-width: 576px)
   -------------------------------------------------------------------------- */
@media screen and (max-width: 576px) {
  .app-container {
    padding: 8px 10px;
    gap: 10px;
  }

  .app-header {
    padding: 10px 12px;
  }

  .brand-icon {
    width: 36px;
    height: 36px;
  }

  .brand-icon svg {
    width: 20px;
    height: 20px;
  }

  .app-header h1 {
    font-size: 1.05rem;
  }

  .subtitle {
    font-size: 0.72rem;
  }

  .mode-btn {
    padding: 6px 3px;
    font-size: 0.72rem;
    gap: 2px;
  }

  .mode-indicator {
    width: 6px;
    height: 6px;
  }

  .mode-cond {
    font-size: 0.64rem;
    padding: 1px 3px;
  }

  .math-expr {
    font-size: 0.95rem;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    padding-bottom: 2px;
  }

  .solution-expr {
    font-size: 0.95rem;
  }

  .formula-subtext {
    font-size: 0.72rem;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }

  .canvas-wrapper {
    height: 260px;
  }

  .chart-legend {
    gap: 8px 10px;
    font-size: 0.7rem;
  }

  .legend-line {
    width: 14px;
  }

  .sim-canvas-container {
    height: 140px;
  }

  .sim-header {
    flex-direction: column;
    align-items: stretch;
    gap: 8px;
  }

  .sim-controls {
    width: 100%;
    justify-content: space-between;
  }

  .scrubber-bar {
    flex-wrap: wrap;
    gap: 6px;
  }

  .time-slider {
    width: 100%;
    order: 3;
  }

  .scrub-label {
    order: 1;
    font-size: 0.72rem;
  }

  .scrub-total {
    order: 2;
    margin-left: auto;
    font-size: 0.72rem;
  }

  .metrics-dashboard {
    grid-template-columns: repeat(2, 1fr);
    gap: 6px;
  }

  .metric-box {
    padding: 8px;
  }

  .metric-value {
    font-size: 1.05rem;
  }

  .metric-name {
    font-size: 0.64rem;
  }

  .metric-desc {
    font-size: 0.62rem;
  }

  .sidebar-panel {
    padding: 12px;
  }

  .label-row {
    font-size: 0.8rem;
  }

  .input-with-unit input[type="number"] {
    width: 50px;
    font-size: 0.8rem;
  }

  .input-with-unit .unit {
    font-size: 0.7rem;
  }

  .action-btn {
    width: 100%;
    justify-content: center;
  }
}

/* --------------------------------------------------------------------------
   6. Extra-Small Mobile Devices (max-width: 400px)
   -------------------------------------------------------------------------- */
@media screen and (max-width: 400px) {
  .app-container {
    padding: 6px 6px;
    gap: 8px;
  }

  .app-header {
    padding: 8px 10px;
  }

  .brand-icon {
    width: 32px;
    height: 32px;
  }

  .brand-icon svg {
    width: 18px;
    height: 18px;
  }

  .app-header h1 {
    font-size: 0.95rem;
  }

  .mode-text {
    font-size: 0.66rem;
  }

  .mode-cond {
    font-size: 0.6rem;
  }

  .canvas-wrapper {
    height: 230px;
  }

  .sim-canvas-container {
    height: 125px;
  }

  .metrics-dashboard {
    grid-template-columns: repeat(2, 1fr);
    gap: 5px;
  }

  .metric-box {
    padding: 6px;
  }

  .metric-value {
    font-size: 0.96rem;
  }

  .vector-legend {
    gap: 6px 8px;
    font-size: 0.68rem;
  }

  .tag-arrow {
    font-size: 0.78rem;
  }
}

/* --------------------------------------------------------------------------
   7. Mobile Devices in Landscape Orientation (max-height: 540px and landscape)
   -------------------------------------------------------------------------- */
@media screen and (max-height: 540px) and (orientation: landscape) {
  .app-container {
    padding: 8px 14px;
    gap: 8px;
  }

  .canvas-wrapper {
    height: 220px;
  }

  .sim-canvas-container {
    height: 120px;
  }

  .sidebar-panel {
    max-height: none;
  }
}

/* --------------------------------------------------------------------------
   8. Touch & Coarse Pointer Accessibility
   -------------------------------------------------------------------------- */
@media screen and (pointer: coarse) {
  .styled-slider::-webkit-slider-thumb {
    width: 20px;
    height: 20px;
  }

  .time-slider::-webkit-slider-thumb {
    width: 18px;
    height: 18px;
  }

  .mode-btn,
  .action-btn,
  .view-tab-btn,
  .toolbar-btn,
  .ctrl-icon-btn,
  .speed-btn {
    min-height: 36px;
  }

  .toggle-item {
    padding: 8px 6px;
  }

  .custom-check {
    width: 18px;
    height: 18px;
  }
}