:root {
  --bg-deep: #0b0d17;
  --panel-bg: rgba(255, 255, 255, 0.04);
  --panel-border: rgba(255, 255, 255, 0.08);
  --accent-cyan: #4fd1ff;
  --accent-pink: #ff6ec7;
  --text-primary: #f2f5ff;
  --text-muted: #9aa3c0;
  --radius: 16px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
}

body {
  min-height: 100vh;
  font-family: -apple-system, "Segoe UI", system-ui, sans-serif;
  background: radial-gradient(circle at 20% 10%, #1a1035 0%, #0b0d17 55%, #05060c 100%);
  color: var(--text-primary);
}

.app {
  max-width: 1200px;
  margin: 0 auto;
  padding: 32px 24px 48px;
}

.app-header {
  text-align: center;
  margin-bottom: 28px;
}

.app-header h1 {
  font-size: 2rem;
  margin: 0 0 8px;
  font-weight: 700;
  letter-spacing: -0.5px;
}

.app-header .accent {
  background: linear-gradient(90deg, var(--accent-cyan), var(--accent-pink));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.subtitle {
  color: var(--text-muted);
  max-width: 640px;
  margin: 0 auto;
  line-height: 1.5;
}

.layout {
  display: grid;
  grid-template-columns: minmax(320px, 560px) minmax(280px, 360px);
  gap: 24px;
  align-items: start;
  justify-content: center;
}

@media (max-width: 880px) {
  .layout { grid-template-columns: 1fr; }
}

.panel {
  background: var(--panel-bg);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  padding: 20px;
  backdrop-filter: blur(10px);
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.35);
}

.canvas-panel {
  display: flex;
  flex-direction: column;
  gap: 14px;
  align-items: center;
}

#canvas-container {
  width: 100%;
  display: flex;
  justify-content: center;
  border-radius: 12px;
  overflow: hidden;
}

#canvas-container canvas {
  display: block;
  border-radius: 12px;
  cursor: crosshair;
}

.stats-bar {
  display: flex;
  gap: 12px;
  width: 100%;
  flex-wrap: wrap;
}

.stat {
  flex: 1;
  min-width: 100px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--panel-border);
  border-radius: 10px;
  padding: 10px 12px;
  text-align: center;
}

.stat-label {
  display: block;
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  margin-bottom: 4px;
}

.stat-value {
  font-size: 1.15rem;
  font-weight: 600;
  font-variant-numeric: tabular-nums;
  color: var(--accent-cyan);
}

#loss-chart {
  width: 100%;
  height: 90px;
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.02);
}

.chart-label {
  margin: 0;
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  align-self: flex-start;
}

.sidebar {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.sidebar h2 {
  font-size: 1rem;
  margin: 0 0 14px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
}

.mode-toggle {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
}

.mode-btn {
  flex: 1;
  padding: 10px;
  border-radius: 10px;
  border: 1px solid var(--panel-border);
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 600;
  transition: all 0.2s ease;
}

.mode-btn.active {
  background: linear-gradient(90deg, rgba(79, 209, 255, 0.18), rgba(255, 110, 199, 0.18));
  color: var(--text-primary);
  border-color: rgba(255, 255, 255, 0.2);
}

.mode-btn:hover { transform: translateY(-1px); }

.control-group { margin-bottom: 16px; }
.control-group.hidden { display: none; }

.primary-btn {
  width: 100%;
  padding: 12px;
  border-radius: 10px;
  border: none;
  cursor: pointer;
  background: linear-gradient(90deg, var(--accent-cyan), var(--accent-pink));
  color: #0b0d17;
  font-weight: 700;
  font-size: 0.9rem;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.primary-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 18px rgba(79, 209, 255, 0.25);
}

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

.hint {
  color: var(--text-muted);
  font-size: 0.78rem;
  margin: 8px 0 0;
}

.slider-label {
  display: block;
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 14px;
}

.slider-label input[type="range"] {
  width: 100%;
  margin-top: 6px;
  accent-color: var(--accent-cyan);
}

.slider-value {
  float: right;
  color: var(--text-primary);
  font-variant-numeric: tabular-nums;
}

.button-row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.button-row button {
  flex: 1;
  min-width: 100px;
  padding: 9px 10px;
  border-radius: 10px;
  border: 1px solid var(--panel-border);
  background: rgba(255, 255, 255, 0.03);
  color: var(--text-primary);
  cursor: pointer;
  font-size: 0.78rem;
  transition: all 0.15s ease;
}

.button-row button:hover {
  background: rgba(255, 255, 255, 0.08);
  transform: translateY(-1px);
}

.formula-card {
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  padding: 16px;
  margin-bottom: 16px;
}

.formula-card .formula {
  font-size: 1.6rem;
  font-weight: 700;
  text-align: center;
  letter-spacing: 0.04em;
  margin-bottom: 10px;
  background: linear-gradient(90deg, var(--accent-cyan), var(--accent-pink));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.formula-card p {
  font-size: 0.85rem;
  color: var(--text-muted);
  line-height: 1.5;
  margin: 0 0 10px;
}

.formula-card .formula-legend {
  list-style: none;
  margin: 0;
  padding: 0;
  font-size: 0.85rem;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.formula-card .formula-legend .var {
  display: inline-block;
  min-width: 20px;
  font-weight: 700;
  color: var(--accent-cyan);
}

.explanation-body {
  font-size: 0.88rem;
  line-height: 1.55;
  color: var(--text-primary);
}

.explanation-body p { margin: 0 0 10px; }

.explanation-body ul.step-list {
  margin: 0 0 10px;
  padding-left: 18px;
}

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

.explanation-body code {
  background: rgba(255, 255, 255, 0.08);
  padding: 1px 6px;
  border-radius: 4px;
}

.app-footer {
  text-align: center;
  margin-top: 36px;
  color: var(--text-muted);
  font-size: 0.78rem;
}