:root {
  --bg: #0c0f14;
  --bg-elevated: #141a24;
  --bg-input: #0e131c;
  --border: rgba(94, 234, 212, 0.12);
  --accent: #5eead4;
  --accent-dim: rgba(94, 234, 212, 0.55);
  --text: #e8edf5;
  --text-muted: #8b98ab;
  --danger: #f87171;
  --font-sans: "DM Sans", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", ui-monospace, monospace;
  --radius: 12px;
  --shadow: 0 24px 48px rgba(0, 0, 0, 0.45);
  --plot-min-height: 640px;
}

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

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.5;
  color: var(--text);
  background:
    radial-gradient(ellipse 120% 80% at 50% -20%, rgba(94, 234, 212, 0.08), transparent),
    radial-gradient(ellipse 80% 50% at 100% 50%, rgba(56, 189, 248, 0.06), transparent),
    var(--bg);
}

main {
  max-width: 1320px;
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
}

header.hero {
  text-align: center;
  margin-bottom: 1rem;
}

header.hero .hero-tagline {
  max-width: 40rem;
  margin: 0.65rem auto 0;
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.55;
}

.page-guide {
  margin-bottom: 1.5rem;
}

.page-guide > h2 {
  margin: 0 0 1rem;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-dim);
}

.page-guide-body {
  text-align: left;
}

header.hero h1 {
  margin: 0 0 0.35rem;
  font-weight: 700;
  font-size: clamp(1.55rem, 4vw, 2.05rem);
  letter-spacing: -0.03em;
  background: linear-gradient(135deg, #f0fdfa 0%, var(--accent) 55%, #38bdf8 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.page-guide-body p {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.58;
}

.page-guide-body .guide-lead {
  font-size: 1rem;
  color: var(--text);
  line-height: 1.62;
}

.page-guide-body .guide-section {
  margin-top: 1.35rem;
  padding-top: 1.15rem;
  border-top: 1px solid var(--border);
}

.page-guide-body .guide-section h2 {
  margin: 0 0 0.55rem;
  font-size: 1.05rem;
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--accent);
}

.page-guide-body ul,
.page-guide-body ol {
  margin: 0.5rem 0 0;
  padding-left: 1.25rem;
  color: var(--text-muted);
  font-size: 0.93rem;
  line-height: 1.55;
}

.page-guide-body li + li {
  margin-top: 0.4rem;
}

.page-guide-body code {
  font-family: var(--font-mono);
  font-size: 0.86em;
  color: var(--accent);
  background: rgba(94, 234, 212, 0.08);
  padding: 0.1em 0.35em;
  border-radius: 4px;
}

.page-guide-body strong {
  color: var(--text);
  font-weight: 600;
}

.workspace {
  display: grid;
  grid-template-columns: minmax(280px, 340px) 1fr;
  gap: 1.25rem;
  align-items: start;
}

@media (max-width: 960px) {
  .workspace {
    grid-template-columns: 1fr;
  }
}

.panel {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.15rem 1.2rem;
  box-shadow: var(--shadow);
}

.panel + .panel {
  margin-top: 1rem;
}

.panel h2 {
  margin: 0 0 0.85rem;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-dim);
}

.field-label {
  display: block;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-dim);
  margin-bottom: 0.35rem;
}

.field-label-spaced {
  margin-top: 0.85rem;
}

select,
input[type="text"],
input[type="number"],
input[type="color"] {
  width: 100%;
  font: inherit;
  color: var(--text);
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.45rem 0.55rem;
}

input[type="color"] {
  height: 2.25rem;
  padding: 0.2rem;
  cursor: pointer;
}

input[type="file"] {
  width: 100%;
  font-size: 0.85rem;
  color: var(--text-muted);
}

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

.control-row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 0.5rem;
  align-items: center;
  margin-top: 0.35rem;
}

.control-row .range-value {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--text-muted);
  min-width: 2.5rem;
  text-align: right;
}

.axis-grid {
  display: grid;
  gap: 0.65rem;
}

.hint,
.status {
  margin: 0.5rem 0 0;
  font-size: 0.82rem;
  color: var(--text-muted);
  line-height: 1.45;
}

.status--error {
  color: var(--danger);
}

.status--ok {
  color: var(--accent);
}

.checkbox-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-top: 0.5rem;
  font-size: 0.88rem;
  color: var(--text-muted);
}

.checkbox-row input {
  width: auto;
  accent-color: var(--accent);
}

.export-row,
.demo-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.75rem;
}

.demo-row {
  margin-top: 0.55rem;
}

.demo-row .btn {
  text-decoration: none;
  text-align: center;
}

.btn {
  font: inherit;
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: rgba(94, 234, 212, 0.12);
  color: var(--accent);
  padding: 0.45rem 0.75rem;
  transition: background 0.15s, border-color 0.15s;
}

.btn:hover {
  background: rgba(94, 234, 212, 0.22);
  border-color: var(--accent-dim);
}

.btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.btn--primary {
  background: var(--accent);
  color: #0c0f14;
  border-color: transparent;
}

.btn--primary:hover {
  background: #7df0de;
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.plot-panel {
  min-height: var(--plot-min-height);
  display: flex;
  flex-direction: column;
}

/* Placeholder and Plotly chart share one cell — not stacked as two separate boxes */
.plot-stage {
  position: relative;
  flex: 1;
  width: 100%;
  min-height: var(--plot-min-height);
}

.plot-stage .plot-placeholder,
.plot-stage .plot-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  min-height: var(--plot-min-height);
  border-radius: 8px;
}

.plot-placeholder {
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 2rem;
  color: var(--text-muted);
  font-size: 0.95rem;
  border: 1px dashed var(--border);
  background: var(--bg-input);
  z-index: 1;
}

.plot-stage .plot-canvas {
  overflow: hidden;
  z-index: 2;
}

.plot-stage:not(.has-plot) .plot-canvas {
  visibility: hidden;
  pointer-events: none;
  z-index: 0;
}

.plot-stage.has-plot .plot-placeholder {
  display: none;
}

.plot-stage.has-plot .plot-canvas {
  visibility: visible;
  pointer-events: auto;
}

.is-hidden {
  display: none !important;
}

.collapsible summary {
  cursor: pointer;
  list-style: none;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-dim);
  margin-bottom: 0.65rem;
}

.collapsible summary::-webkit-details-marker {
  display: none;
}

.collapsible summary::after {
  content: " ▾";
  font-size: 0.65rem;
}

.collapsible[open] summary::after {
  content: " ▴";
}

.two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.65rem;
}

@media (max-width: 400px) {
  .two-col {
    grid-template-columns: 1fr;
  }
}