/* ==========================================================================
   Spider with Axioms, HTML presentation styles
   Single-file CSS, no framework. Dark theme, harmonised with portfolio.
   ========================================================================== */

/* ---- design tokens ----------------------------------------------------- */
:root {
  --bg:           #0c0a14;
  --surface:      #13111c;
  --surface-2:    #1a1825;
  --ink:          #f1f5f9;
  --soft-ink:     #cbd5e1;
  --muted:        #94a3b8;
  --rule:         #2d2a3e;
  --rule-strong:  #3f3b58;

  --ax:           #34d399;
  --ax-bg:        rgba(52, 211, 153, .10);
  --ax-border:    rgba(52, 211, 153, .35);
  --noax:         #f87171;
  --noax-bg:      rgba(248, 113, 113, .10);
  --noax-border:  rgba(248, 113, 113, .35);

  --grad-1:       #818cf8;       /* indigo  */
  --grad-2:       #a78bfa;       /* violet  */
  --grad-3:       #22d3ee;       /* cyan    */

  --term-bg:      #0a0814;
  --term-fg:      #d6dbe4;
  --modal-bg:     var(--surface);

  --font-sans:    -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
                  "Helvetica Neue", Arial, sans-serif;
  --font-mono:    "JetBrains Mono", "Fira Code", "SF Mono", Consolas,
                  "Liberation Mono", monospace;

  --radius:       10px;
  --radius-lg:    14px;
  --pad:          clamp(1rem, 2.4vw, 2.2rem);
}

/* ---- reset / base ------------------------------------------------------ */
*, *::before, *::after { box-sizing: border-box; }
html, body { margin: 0; padding: 0; height: 100%; }
body {
  font-family: var(--font-sans);
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  overflow: hidden;
}
code { font-family: var(--font-mono); color: var(--soft-ink); }
button { font: inherit; cursor: pointer; }
hr { border: 0; }
a { color: var(--grad-1); text-decoration: none; }
a:hover { color: var(--grad-3); text-decoration: underline; }

/* ---- top labelled nav -------------------------------------------------- */
#nav {
  position: fixed;
  top: 1rem; left: 50%;
  transform: translateX(-50%);
  display: flex; gap: 0.35rem;
  padding: 0.35rem;
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: 999px;
  z-index: 30;
  box-shadow: 0 4px 16px rgb(0 0 0 / 30%);
}
.nav-tab {
  background: transparent;
  border: 0;
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 600;
  padding: 0.45rem 0.9rem;
  border-radius: 999px;
  display: inline-flex; align-items: center; gap: 0.4rem;
  transition: color 120ms ease, background 120ms ease;
}
.nav-tab:hover { color: var(--ink); }
.nav-tab .nav-num {
  display: inline-grid; place-items: center;
  width: 1.1rem; height: 1.1rem;
  border-radius: 50%;
  font-size: 0.7rem;
  background: var(--rule);
  color: var(--soft-ink);
}
.nav-tab.active {
  color: #fff;
  background: linear-gradient(135deg, var(--grad-1), var(--grad-2));
}
.nav-tab.active .nav-num {
  background: rgba(255,255,255,.18);
  color: #fff;
}

/* ---- side arrows ------------------------------------------------------- */
.nav-arrow {
  position: fixed;
  top: 50%;
  transform: translateY(-50%);
  width: 44px; height: 44px;
  display: grid; place-items: center;
  background: var(--surface);
  border: 1px solid var(--rule);
  color: var(--soft-ink);
  border-radius: 50%;
  z-index: 25;
  font-size: 1.4rem; line-height: 1;
  opacity: 0.45;
  transition: opacity 150ms ease, transform 150ms ease, color 150ms ease;
}
.nav-arrow:hover { opacity: 1; color: var(--ink); transform: translateY(-50%) scale(1.06); }
.nav-arrow.left  { left: 0.9rem; }
.nav-arrow.right { right: 0.9rem; }
.nav-arrow[disabled] { opacity: 0.15; cursor: not-allowed; }

/* ---- footer chrome ----------------------------------------------------- */
#chrome {
  position: fixed; left: 0; right: 0; bottom: 0;
  display: flex; justify-content: space-between;
  padding: 0.65rem 1.4rem;
  color: var(--muted); font-size: 0.78rem;
  pointer-events: none;
  z-index: 30;
}

/* ---- slide host -------------------------------------------------------- */
#deck { height: 100%; }
.slide {
  position: absolute; inset: 0;
  padding: calc(var(--pad) + 3.2rem) calc(var(--pad) + 3rem) calc(var(--pad) + 0.6rem);
  display: none;
  overflow-y: auto;
  animation: fade-in 220ms ease;
}
.slide.active { display: block; }
@keyframes fade-in { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; } }

/* ---- generic slide chrome --------------------------------------------- */
.eyebrow {
  margin: 0 0 0.35rem;
  font-size: 0.72rem; font-weight: 700;
  color: var(--grad-1);
  letter-spacing: 0.18em; text-transform: uppercase;
}
.slide-header h2,
.slide h1, .slide h2 {
  margin: 0 0 0.4rem;
  font-weight: 700;
  color: var(--ink);
  line-height: 1.1;
}
.slide h2 { font-size: clamp(1.5rem, 2.6vw, 2.0rem); }
.accent-rule {
  width: 2.2rem; height: 3px;
  background: linear-gradient(90deg, var(--grad-1), var(--grad-3));
  border-radius: 2px;
  margin: 0.5rem 0 0.9rem;
}
.lede {
  margin: 0 0 1.2rem;
  font-size: clamp(0.95rem, 1.2vw, 1.05rem);
  color: var(--soft-ink);
  max-width: 70ch;
}

/* gradient text helper */
.gradient-text {
  background: linear-gradient(135deg, var(--grad-1), var(--grad-2), var(--grad-3));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

/* ==========================================================================
   SLIDE 1, title
   ========================================================================== */
.slide--title { padding: 0; }
.slide--title::before {
  content: "";
  position: absolute; top: 0; bottom: 0; left: 0;
  width: 5px;
  background: linear-gradient(180deg, var(--grad-1), var(--grad-3));
}

.back-to-projects {
  position: absolute;
  top: 1.4rem;
  left: 2rem;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 1rem;
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: 999px;
  color: var(--soft-ink);
  font-size: 0.85rem;
  font-weight: 500;
  z-index: 25;
  transition: border-color 150ms ease, color 150ms ease;
}
.back-to-projects:hover {
  border-color: var(--grad-1);
  color: var(--ink);
  text-decoration: none;
}
.title-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr;
  gap: 2.5rem;
  height: 100%;
  padding: 5rem 4.5rem 5.5rem;
  align-items: center;
}
.title-text h1 {
  font-size: clamp(2.4rem, 5vw, 4.4rem);
  letter-spacing: -0.01em;
  margin: 0 0 0.8rem;
}
.title-text .subtitle {
  font-size: clamp(1.05rem, 1.6vw, 1.4rem);
  color: var(--soft-ink);
  max-width: 32ch;
  margin: 0;
}
.title-text .author { font-size: 1.05rem; font-weight: 700; margin: 0; color: var(--ink); }
.title-text .meta   { font-size: 0.95rem; color: var(--muted); margin: 0.15rem 0 0; }
.title-text .accent-rule { margin: 1.6rem 0 1.1rem; width: 3rem; }

.title-stack {
  display: flex; flex-direction: column; gap: 0.6rem;
  align-self: center;
}
.badge {
  padding: 0.85rem 1.1rem;
  border-radius: var(--radius);
  font-weight: 700; color: #fff;
  font-size: clamp(0.95rem, 1.2vw, 1.1rem);
}
.badge--noax { background: var(--noax); width: 100%; }
.badge--ax   { background: var(--ax);   width: 72%;  }
.badge-caption {
  margin: 0.4rem 0 0;
  font-size: 0.85rem; font-style: italic; color: var(--muted);
}

.title-info-card {
  align-self: center;
  padding: 1.1rem 1.3rem 1.2rem;
  background: var(--surface);
  border: 1px solid var(--rule);
  border-left: 3px solid var(--grad-1);
  border-radius: var(--radius);
}
.title-info-card h3 {
  margin: 0 0 0.45rem;
  font-size: 1.0rem;
  font-weight: 700;
  color: var(--ink);
}
.title-info-card p {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.55;
  color: var(--soft-ink);
}
.title-info-card .report-prompt {
  margin-top: 0.85rem;
  color: var(--muted);
  font-size: 0.88rem;
}
.title-info-card .report-link {
  margin-top: 0.55rem;
}

/* ==========================================================================
   SLIDE 2, introduction cards
   ========================================================================== */
.intro-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  max-width: 1100px;
  margin: 0 auto;
}
.intro-card {
  background: var(--surface);
  border: 1px solid var(--rule);
  border-left: 3px solid var(--grad-1);
  border-radius: var(--radius);
  padding: 1.1rem 1.3rem;
}
.intro-card h3 {
  margin: 0 0 0.5rem;
  font-size: 1.0rem;
  font-weight: 700;
  color: var(--ink);
}
.intro-card p {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.55;
  color: var(--soft-ink);
}
.intro-card code {
  color: var(--grad-3);
  font-size: 0.88em;
}
.intro-card.span-2 { grid-column: 1 / -1; }
.intro-card .card-links {
  margin-top: 0.55rem;
  font-size: 0.9rem;
  color: var(--soft-ink);
}
.intro-card .card-links a { color: var(--grad-1); }
.intro-card .card-links a:hover { color: var(--grad-3); }

/* tiny SVG illustration block inside Spider card */
.intro-svg {
  display: block;
  margin: 0.7rem 0;
  width: 100%;
  max-width: 280px;
}

/* ==========================================================================
   SLIDE 3, accordion (code comparisons)
   ========================================================================== */
.accordion {
  display: flex; flex-direction: column;
  gap: 0.75rem;
  max-width: 1280px;
  margin: 0 auto;
}
.cmp {
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  background: var(--surface);
  transition: box-shadow 150ms ease, border-color 150ms ease;
}
.cmp[open] {
  box-shadow: 0 4px 20px rgb(0 0 0 / 40%);
  border-color: var(--grad-1);
}
.cmp summary {
  list-style: none;
  display: flex; align-items: center; gap: 0.9rem;
  padding: 0.85rem 1.1rem;
  cursor: pointer;
  font-size: 1.02rem;
  user-select: none;
}
.cmp summary::-webkit-details-marker { display: none; }
.cmp-num {
  display: inline-grid; place-items: center;
  width: 1.7rem; height: 1.7rem;
  border-radius: 50%;
  background: var(--surface-2); color: var(--soft-ink);
  font-weight: 700; font-size: 0.85rem;
}
.cmp[open] .cmp-num {
  background: linear-gradient(135deg, var(--grad-1), var(--grad-2));
  color: #fff;
}
.cmp-title { color: var(--ink); font-weight: 600; flex-shrink: 0; }
.cmp-title code { font-size: 0.95em; color: var(--grad-3); }
.cmp-hint {
  color: var(--muted);
  font-size: 0.88rem;
  font-style: italic;
  flex: 1; text-align: right;
}
.cmp-caption {
  margin: 0 1.1rem 0.6rem;
  padding: 0.6rem 0.9rem;
  background: var(--surface-2);
  border-left: 2px solid var(--grad-1);
  border-radius: 6px;
  font-size: 0.92rem;
  color: var(--soft-ink);
}

.cmp-cols {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
  padding: 0 1.1rem 1.1rem;
}
.code {
  margin: 0;
  padding: 0.85rem 1rem;
  border-radius: var(--radius);
  font-family: var(--font-mono);
  font-size: 0.78rem;
  line-height: 1.45;
  overflow-x: auto;
  white-space: pre;
  border: 1px solid;
  color: var(--soft-ink);
}
.code--noax { background: var(--noax-bg); border-color: var(--noax-border); }
.code--ax   { background: var(--ax-bg);   border-color: var(--ax-border); }


/* ==========================================================================
   SLIDE 4, live demo
   ========================================================================== */
.task-card {
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 0.95rem 1.1rem;
  margin: 0 auto 1rem;
  max-width: 1280px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.9rem 1.6rem;
}
.task-card .task-section h4 {
  margin: 0 0 0.45rem;
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--muted);
  letter-spacing: 0.15em;
  text-transform: uppercase;
}
.task-card .task-row {
  font-size: 0.9rem; color: var(--soft-ink);
  margin: 0 0 0.2rem;
}
.task-card .task-row .k { color: var(--muted); margin-right: 0.4rem; }
.task-card .task-row code { color: var(--grad-3); }
.task-card a {
  display: inline-flex; align-items: center; gap: 0.25rem;
  font-size: 0.88rem;
  color: var(--grad-1);
}
.task-card a:hover { color: var(--grad-3); }

.demo-controls {
  display: flex; align-items: center;
  gap: 1rem;
  margin: 0 auto 1rem;
  max-width: 1280px;
}
.btn-primary {
  background: linear-gradient(135deg, var(--grad-1), var(--grad-2));
  color: #fff; border: 0;
  padding: 0.7rem 1.4rem;
  font-size: 1.0rem; font-weight: 600;
  border-radius: var(--radius);
  transition: filter 150ms ease, transform 80ms ease;
}
.btn-primary:hover  { filter: brightness(1.1); }
.btn-primary:active { transform: translateY(1px); }
.btn-primary:disabled{ background: var(--rule); color: var(--muted); cursor: not-allowed; }

.btn-secondary {
  background: transparent; color: var(--soft-ink);
  border: 1px solid var(--rule);
  padding: 0.65rem 1.1rem; font-size: 0.95rem;
  border-radius: var(--radius);
}
.btn-secondary:hover { border-color: var(--grad-1); color: var(--ink); }

.demo-status {
  color: var(--muted); font-size: 0.92rem;
  font-style: italic;
}

.demo-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  max-width: 1280px;
  margin: 0 auto;
}
.demo-pane {
  display: flex; flex-direction: column;
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--surface);
}
.pane-header {
  display: flex; justify-content: space-between; align-items: center;
  padding: 0.55rem 0.95rem;
  color: #fff;
  font-weight: 600;
  font-size: 0.92rem;
}
.pane-header--noax { background: var(--noax); }
.pane-header--ax   { background: var(--ax); color: #052e25; }
.pane-header a {
  color: inherit; opacity: 0.85; font-size: 0.82rem; font-weight: 500;
}
.pane-header a:hover { opacity: 1; text-decoration: underline; }
.pane-timer {
  font-family: var(--font-mono); font-size: 0.85rem;
  background: rgb(0 0 0 / 22%);
  padding: 0.15rem 0.5rem;
  border-radius: 4px;
}
.pane-header--ax .pane-timer { background: rgb(0 0 0 / 14%); color: #052e25; }
.pane-term {
  margin: 0;
  background: var(--term-bg);
  color: var(--term-fg);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  line-height: 1.45;
  height: 300px;
  overflow-y: auto;
  padding: 0.8rem 0.95rem;
  white-space: pre;
}
.pane-term .line-info { color: var(--term-fg); }
.pane-term .line-stat { color: var(--ax); }

/* shared comparison panel (single panel, replaces twin summaries) */
.compare-panel {
  display: none;
  margin: 1rem auto 0;
  max-width: 1280px;
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 1.2rem 1.4rem;
}
.compare-panel.is-visible { display: block; }
.compare-headline {
  text-align: center;
  font-size: clamp(1.4rem, 2.4vw, 2rem);
  font-weight: 800;
  letter-spacing: -0.01em;
  margin: 0 0 0.4rem;
}
.compare-subline {
  text-align: center;
  font-size: 0.92rem;
  color: var(--muted);
  margin: 0 0 1.2rem;
}
.compare-grid {
  display: grid;
  grid-template-columns: 11rem 1fr 1fr;
  gap: 0.55rem 0.8rem;
  align-items: center;
}
.compare-grid .ch-label {
  font-size: 0.85rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.compare-grid .ch-bar-cell { position: relative; }
.compare-grid .ch-bar {
  height: 22px;
  border-radius: 4px;
  position: relative;
  background: var(--surface-2);
  overflow: hidden;
}
.compare-grid .ch-bar-fill {
  height: 100%;
  width: 0;
  transition: width 700ms cubic-bezier(.2, .7, .25, 1);
  border-radius: 4px;
}
.compare-grid .ch-bar-fill.noax { background: var(--noax); }
.compare-grid .ch-bar-fill.ax   { background: var(--ax); }
.compare-grid .ch-bar-value {
  position: absolute; right: 0.55rem; top: 50%;
  transform: translateY(-50%);
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--ink);
  text-shadow: 0 0 4px rgb(0 0 0 / 55%);
  font-weight: 600;
}
.compare-grid .ch-header { font-size: 0.7rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.1em; text-align: center; }
.compare-grid .ch-header.noax { color: var(--noax); }
.compare-grid .ch-header.ax   { color: var(--ax); }
.equal-row .ch-bar-fill { width: 50% !important; }
.equal-row::after {
  content: " same optimal cost (equivalence check passes)";
  grid-column: 1 / -1;
  font-size: 0.78rem;
  color: var(--ax);
  font-style: italic;
  padding-left: 0.2rem;
  margin-top: 0.1rem;
}

/* ==========================================================================
   SLIDE 5, results (existing charts)
   ========================================================================== */
.charts {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.4rem;
  max-width: 1280px;
  margin: 0 auto 1rem;
}
.chart-card {
  margin: 0;
  padding: 1.1rem 1.2rem 1rem;
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
}
.chart-title {
  margin: 0 0 0.55rem;
  font-size: 1.0rem; font-weight: 700; color: var(--ink);
}
.chart-host {
  width: 100%;
  height: 280px;
}
.chart-legend {
  display: flex; flex-wrap: wrap; gap: 0.6rem 1.4rem;
  margin: 0.55rem 0 0.4rem;
  font-size: 0.82rem; color: var(--soft-ink);
  align-items: center;
}
.swatch {
  display: inline-block; width: 14px; height: 14px;
  border-radius: 3px; margin-right: 0.35rem; vertical-align: middle;
}
.swatch--noax { background: var(--noax); }
.swatch--ax   { background: var(--ax); }
.chart-caption {
  margin: 0.4rem 0 0;
  font-size: 0.88rem;
  color: var(--soft-ink);
}
.chart-caption strong { color: var(--ink); }
.chart-note {
  margin: 0.4rem 0 0;
  font-size: 0.88rem;
  color: var(--soft-ink);
}
.chart-note strong { color: var(--ink); }

.results-footnote {
  max-width: 1280px;
  margin: 0.6rem auto 0;
  padding: 0.75rem 1rem;
  background: var(--surface-2);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  font-size: 0.85rem;
  color: var(--soft-ink);
}
.results-footnote strong { color: var(--ink); }

/* ==========================================================================
   SVG chart styling
   ========================================================================== */
.svgchart text { fill: var(--soft-ink); font-family: var(--font-sans); font-size: 10px; }
.svgchart .axis-line { stroke: var(--rule); stroke-width: 1; }
.svgchart .grid-line { stroke: var(--rule); stroke-width: 0.5; stroke-dasharray: 2 2; }
.svgchart .label--muted { fill: var(--muted); font-size: 9px; }
.svgchart .bar-noax { fill: var(--noax); }
.svgchart .bar-ax   { fill: var(--ax); }
.svgchart .bar-label { fill: var(--ink); font-size: 9px; font-weight: 600; }
.svgchart .speedup   { fill: var(--ax); font-weight: 700; font-size: 10px; }
.svgchart .group-label {
  fill: var(--muted); font-size: 9px; text-transform: uppercase;
  letter-spacing: 0.05em; font-weight: 600;
}
.svgchart .group-divider { stroke: var(--rule); stroke-width: 1; stroke-dasharray: 3 3; }

/* ==========================================================================
   Info popover (Fast Downward and other glossary terms)
   ========================================================================== */
.info-btn {
  display: inline-grid; place-items: center;
  width: 1.2rem; height: 1.2rem;
  margin-left: 0.25rem;
  background: var(--rule);
  color: var(--soft-ink);
  border: 0;
  border-radius: 50%;
  font-size: 0.72rem; font-weight: 700; font-style: italic;
  font-family: serif;
  cursor: pointer;
  vertical-align: baseline;
  transition: background 120ms ease, color 120ms ease;
}
.info-btn:hover { background: var(--grad-1); color: #fff; }

.about-site-btn {
  position: fixed;
  top: 1.4rem;
  right: 2rem;
  width: auto;
  height: auto;
  margin-left: 0;
  padding: 0.5rem 1rem;
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: 999px;
  color: var(--soft-ink);
  font-family: inherit;
  font-style: normal;
  font-size: 0.85rem;
  font-weight: 500;
  z-index: 25;
  transition: border-color 150ms ease, color 150ms ease;
}
.about-site-btn:hover {
  background: var(--surface);
  border-color: var(--grad-1);
  color: var(--ink);
}

#info-popover {
  position: absolute;
  z-index: 80;
  width: 320px;
  background: var(--surface);
  border: 1px solid var(--rule-strong);
  border-radius: var(--radius);
  padding: 0.85rem 1rem;
  box-shadow: 0 12px 36px rgb(0 0 0 / 55%);
  font-size: 0.88rem;
  color: var(--soft-ink);
}
#info-popover[hidden] { display: none; }
#info-popover h4 {
  margin: 0 0 0.35rem;
  color: var(--ink);
  font-size: 0.98rem;
}
#info-popover p { margin: 0 0 0.6rem; line-height: 1.5; }
#info-popover .popover-link {
  font-size: 0.84rem;
  display: inline-flex; align-items: center; gap: 0.3rem;
}

/* ==========================================================================
   Report download link
   ========================================================================== */
.report-link {
  display: inline-flex; align-items: center; gap: 0.4rem;
  padding: 0.45rem 0.85rem;
  background: var(--surface-2);
  border: 1px solid var(--rule);
  border-radius: 999px;
  color: var(--soft-ink);
  font-size: 0.82rem; font-weight: 500;
  transition: border-color 150ms ease, color 150ms ease;
}
.report-link:hover {
  border-color: var(--grad-1);
  color: var(--ink);
  text-decoration: none;
}

/* (report-link now lives inside .title-info-card on slide 1, no special
   placement needed) */

/* ==========================================================================
   Modal (rate-limit / server-busy)
   ========================================================================== */
.modal-overlay {
  position: fixed; inset: 0;
  z-index: 100;
  display: grid; place-items: center;
  background: rgb(2 4 8 / 65%);
  backdrop-filter: blur(4px);
  animation: modal-fade-in 180ms ease;
  padding: 1rem;
}
@keyframes modal-fade-in { from { opacity: 0; } to { opacity: 1; } }
.modal-overlay[hidden] { display: none; }

.modal-card {
  max-width: 460px;
  background: var(--modal-bg);
  border: 1px solid var(--rule-strong);
  border-radius: var(--radius-lg);
  padding: 1.6rem 1.8rem 1.4rem;
  box-shadow: 0 18px 60px rgb(0 0 0 / 55%);
  text-align: center;
}
.modal-title {
  margin: 0 0 0.6rem;
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--ink);
}
.modal-body {
  margin: 0 0 1.2rem;
  font-size: 0.98rem;
  line-height: 1.5;
  color: var(--soft-ink);
}
.modal-actions {
  display: flex;
  justify-content: center;
}
.modal-actions .btn-primary {
  background: linear-gradient(135deg, var(--grad-1), var(--grad-2));
  color: #fff;
  border: 0;
  padding: 0.55rem 1.4rem;
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: var(--radius);
  cursor: pointer;
}
.modal-actions .btn-primary:hover { filter: brightness(1.1); }

/* ---- responsive tighteners -------------------------------------------- */
@media (max-width: 1024px) {
  .title-grid { grid-template-columns: 1fr; padding: 3rem; }
  .demo-grid, .charts, .cmp-cols, .intro-grid, .task-card { grid-template-columns: 1fr; }
  .pane-term { height: 220px; }
  .compare-grid { grid-template-columns: 7rem 1fr 1fr; }
  #nav { gap: 0.15rem; padding: 0.25rem; }
  .nav-tab { padding: 0.35rem 0.55rem; font-size: 0.72rem; }
  .nav-arrow { width: 36px; height: 36px; }
}