:root {
  --bg: #f4efe6;
  --bg-accent: #dfefe6;
  --paper: rgba(255, 251, 245, 0.85);
  --paper-strong: #fffaf2;
  --ink: #19323c;
  --muted: #60727a;
  --line: rgba(25, 50, 60, 0.12);
  --teal: #0c7c82;
  --teal-soft: rgba(12, 124, 130, 0.16);
  --coral: #dc6b43;
  --gold: #d4a64f;
  --shadow: 0 18px 40px rgba(39, 57, 66, 0.12);
  --radius-xl: 28px;
  --radius-lg: 20px;
  --radius-md: 14px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  font-family: "PingFang SC", "Microsoft YaHei", "Segoe UI", sans-serif;
  background:
    radial-gradient(circle at top left, rgba(212, 166, 79, 0.22), transparent 28%),
    radial-gradient(circle at 85% 10%, rgba(12, 124, 130, 0.18), transparent 22%),
    linear-gradient(135deg, var(--bg) 0%, #f8f5ef 45%, var(--bg-accent) 100%);
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(255, 255, 255, 0.08) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.08) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: linear-gradient(to bottom, rgba(0, 0, 0, 0.35), transparent 70%);
}

.page-shell {
  width: min(1360px, calc(100% - 32px));
  margin: 0 auto;
  padding: 32px 0 48px;
}

.hero,
.stage-card,
.panel-card,
.basis-card {
  position: relative;
  overflow: hidden;
  border: 1px solid rgba(255, 255, 255, 0.5);
  border-radius: var(--radius-xl);
  background: var(--paper);
  box-shadow: var(--shadow);
  backdrop-filter: blur(14px);
}

.hero {
  display: flex;
  justify-content: space-between;
  gap: 24px;
  padding: 28px 30px;
  margin-bottom: 24px;
}

.hero::after,
.panel-card::after,
.stage-card::after,
.basis-card::after {
  content: "";
  position: absolute;
  inset: auto -60px -80px auto;
  width: 200px;
  height: 200px;
  border-radius: 999px;
  background: radial-gradient(circle, rgba(12, 124, 130, 0.12), transparent 70%);
}

.hero-copy h1,
.card-topline h2 {
  margin: 0;
  font-family: Georgia, "Times New Roman", serif;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.hero-copy h1 {
  font-size: clamp(2rem, 3vw, 3.4rem);
}

.eyebrow,
.section-kicker {
  margin: 0 0 10px;
  font-size: 0.78rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--teal);
}

.hero-text,
.section-tip,
.note-block p {
  color: var(--muted);
}

.hero-badges {
  display: flex;
  flex-wrap: wrap;
  align-content: flex-start;
  justify-content: flex-end;
  gap: 10px;
  min-width: 280px;
}

.badge,
.value-pill,
.knot-chip,
.term-chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  border-radius: 999px;
  padding: 8px 12px;
  font-size: 0.92rem;
}

.badge {
  background: rgba(255, 255, 255, 0.68);
  border: 1px solid rgba(25, 50, 60, 0.08);
}

.layout {
  display: grid;
  grid-template-columns: minmax(0, 2fr) minmax(320px, 420px);
  gap: 24px;
  align-items: start;
}

.stage-card,
.basis-card {
  padding: 22px;
}

.side-panel {
  display: grid;
  gap: 20px;
}

.panel-card {
  padding: 20px;
}

.card-topline {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: start;
  margin-bottom: 18px;
}

.card-topline h2 {
  font-size: 1.45rem;
}

.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 16px;
}

.action-btn {
  border: 0;
  border-radius: 999px;
  padding: 11px 18px;
  font-size: 0.96rem;
  color: var(--ink);
  background: rgba(255, 255, 255, 0.84);
  box-shadow: inset 0 0 0 1px rgba(25, 50, 60, 0.08);
  cursor: pointer;
  transition: transform 150ms ease, box-shadow 150ms ease, background 150ms ease;
}

.action-btn:hover {
  transform: translateY(-1px);
  box-shadow: inset 0 0 0 1px rgba(25, 50, 60, 0.12), 0 10px 18px rgba(25, 50, 60, 0.08);
}

.action-btn-primary {
  color: white;
  background: linear-gradient(135deg, var(--teal), #0b9da4);
}

.action-btn-ghost {
  background: rgba(220, 107, 67, 0.12);
  color: #8f4227;
}

.action-btn:disabled {
  cursor: not-allowed;
  opacity: 0.45;
  transform: none;
  box-shadow: inset 0 0 0 1px rgba(25, 50, 60, 0.06);
}

.stage-wrap,
.basis-wrap {
  border-radius: calc(var(--radius-xl) - 8px);
  overflow: hidden;
  border: 1px solid rgba(25, 50, 60, 0.08);
  background:
    radial-gradient(circle at top, rgba(255, 255, 255, 0.9), rgba(246, 247, 244, 0.92)),
    linear-gradient(180deg, rgba(255, 255, 255, 0.9), rgba(239, 242, 238, 0.9));
}

.curve-svg,
.basis-svg {
  display: block;
  width: 100%;
  height: auto;
}

.control-group {
  margin-bottom: 18px;
}

.control-group label,
.mini-title,
.stat-label {
  display: block;
  margin-bottom: 8px;
  font-size: 0.86rem;
  color: var(--muted);
}

.range-row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 12px;
  align-items: center;
}

input[type="range"] {
  width: 100%;
  accent-color: var(--teal);
}

.value-pill {
  min-width: 64px;
  justify-content: center;
  background: rgba(12, 124, 130, 0.12);
  color: var(--teal);
}

.stat-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.stat-card {
  padding: 14px;
  border-radius: var(--radius-md);
  background: rgba(255, 255, 255, 0.72);
  border: 1px solid rgba(25, 50, 60, 0.08);
}

.stat-card strong {
  display: block;
  font-size: 1.02rem;
  line-height: 1.4;
}

.formula-block {
  padding: 14px 16px;
  border-radius: var(--radius-lg);
  background: rgba(255, 255, 255, 0.7);
  border: 1px solid rgba(25, 50, 60, 0.08);
}

.formula-main,
.formula-sub {
  margin: 0;
  line-height: 1.75;
}

.formula-main {
  font-size: 1.16rem;
  font-family: Georgia, "Times New Roman", serif;
}

.formula-sub + .formula-sub,
.formula-main + .formula-sub {
  margin-top: 10px;
}

.sigma {
  font-size: 1.6em;
  vertical-align: middle;
}

.note-block {
  margin-top: 14px;
}

.basis-terms,
.knot-vector {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.term-chip,
.knot-chip {
  border: 1px solid rgba(25, 50, 60, 0.08);
  background: rgba(255, 255, 255, 0.76);
}

.term-chip {
  padding-right: 14px;
}

.term-color {
  width: 12px;
  height: 12px;
  border-radius: 999px;
  display: inline-block;
}

.knot-wrap {
  margin-top: 14px;
}

.mini-title {
  margin-bottom: 10px;
}

.axis-text,
.point-label,
.curve-caption,
.basis-label {
  font-family: "Segoe UI", "Microsoft YaHei", sans-serif;
}

.grid-line {
  stroke: rgba(25, 50, 60, 0.08);
  stroke-width: 1;
}

.grid-line-strong {
  stroke: rgba(25, 50, 60, 0.14);
}

.axis-text {
  fill: #73858d;
  font-size: 14px;
}

.control-polygon {
  fill: none;
  stroke: rgba(25, 50, 60, 0.28);
  stroke-width: 3;
  stroke-dasharray: 10 10;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.curve-path {
  fill: none;
  stroke: var(--coral);
  stroke-width: 6;
  stroke-linecap: round;
  stroke-linejoin: round;
  filter: url(#softGlow);
}

.control-point-hit {
  fill: transparent;
  cursor: grab;
}

.control-point-ring {
  stroke: white;
  stroke-width: 3;
}

.control-point.selected .control-point-core {
  stroke: var(--ink);
  stroke-width: 3;
}

.control-point.selected .control-point-ring {
  stroke: rgba(255, 255, 255, 0.98);
  stroke-width: 5;
}

.point-label,
.curve-caption,
.basis-label {
  fill: var(--ink);
  font-size: 14px;
  font-weight: 600;
}

.curve-caption {
  font-size: 15px;
}

.current-guide {
  stroke: rgba(12, 124, 130, 0.5);
  stroke-width: 2;
  stroke-dasharray: 7 7;
}

.current-dot {
  fill: var(--gold);
  stroke: white;
  stroke-width: 3;
}

.basis-path {
  fill: none;
  stroke-width: 4;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.basis-marker {
  fill: rgba(220, 107, 67, 0.9);
  stroke: white;
  stroke-width: 3;
}

.basis-line {
  stroke: rgba(220, 107, 67, 0.45);
  stroke-width: 2.5;
  stroke-dasharray: 8 7;
}

@media (max-width: 1080px) {
  .layout {
    grid-template-columns: 1fr;
  }

  .hero {
    flex-direction: column;
  }

  .hero-badges {
    justify-content: flex-start;
    min-width: 0;
  }
}

@media (max-width: 680px) {
  .page-shell {
    width: min(100% - 20px, 1360px);
    padding-top: 18px;
  }

  .hero,
  .stage-card,
  .panel-card,
  .basis-card {
    border-radius: 22px;
  }

  .toolbar,
  .stat-grid {
    grid-template-columns: 1fr;
  }

  .toolbar {
    display: grid;
  }

  .card-topline {
    flex-direction: column;
  }
}