/* ML Visualizer landing page
   Design tokens: dark plotting canvas + two class-accent colors
   (mirrors the two-class scatter/decision-boundary convention used
   throughout the app itself), serif display / sans body / mono data. */

:root {
  --canvas: #0f1420;
  --panel: #161c2c;
  --panel-raised: #1b2236;
  --rule: #262e44;
  --ink: #edeff5;
  --muted: #8e96ac;
  --signal: #ff8a3d;
  --signal-dim: #a85f2e;
  --contrast: #46c9c0;

  --font-display: Georgia, "Iowan Old Style", "Palatino Linotype", ui-serif, serif;
  --font-body: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial,
    sans-serif;
  --font-mono: ui-monospace, "SF Mono", "Cascadia Code", "Segoe UI Mono", Consolas,
    "Liberation Mono", monospace;

  --max-w: 72rem;
  --radius: 4px;
}

* {
  box-sizing: border-box;
}

html {
  color-scheme: dark;
}

body {
  margin: 0;
  background: var(--canvas);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

img,
svg,
canvas {
  display: block;
  max-width: 100%;
}

a {
  color: inherit;
}

a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--signal);
  outline-offset: 3px;
}

/* Off-screen until focused, so keyboard/screen-reader users can bypass the
   topbar instead of tabbing through brand mark + 4 nav links every load.
   Transform, not top, stays off the layout-animation list above. */
.skip-link {
  position: absolute;
  top: 1rem;
  left: 1rem;
  z-index: 100;
  background: var(--signal);
  color: #1a0f05;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 0.6rem 1rem;
  border-radius: 3px;
  text-decoration: none;
  transform: translateY(-4rem);
  transition: transform 0.15s ease;
}

.skip-link:focus {
  transform: translateY(0);
}

.eyebrow {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--signal);
  font-variant-numeric: tabular-nums;
}

h1,
h2,
h3 {
  font-family: var(--font-display);
  font-weight: 400;
  text-wrap: balance;
  margin: 0;
}

.wrap {
  max-width: var(--max-w);
  margin-inline: auto;
  padding-inline: 1.5rem;
}

/* ---------- Topbar ---------- */

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--canvas);
  border-bottom: 1px solid var(--rule);
}

.topbar .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding-block: 0.85rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-family: var(--font-mono);
  font-size: 0.95rem;
  letter-spacing: 0.01em;
  text-decoration: none;
  color: var(--ink);
  white-space: nowrap;
}

.brand .mark {
  width: 22px;
  height: 22px;
  flex: none;
}

.brand-parent {
  color: var(--muted);
}

.brand-sep {
  color: var(--rule);
  margin-inline: 0.35rem;
}

.brand:hover .brand-parent {
  color: var(--ink);
}

.topbar nav {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

.topbar nav a.text-link {
  font-size: 0.9rem;
  color: var(--muted);
  text-decoration: none;
}

.topbar nav a.text-link:hover {
  color: var(--ink);
}

/* Narrow viewports: keep the topbar on one line by dropping the
   secondary nav links; the same targets remain in the footer. */
@media (max-width: 860px) {
  .topbar nav a.text-link {
    display: none;
  }
}

@media (max-width: 640px) {
  .brand-parent,
  .brand-sep {
    display: none;
  }
}

/* ---------- Buttons ---------- */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  text-decoration: none;
  border-radius: 3px;
  padding: 0.65rem 1.15rem;
  border: 1px solid transparent;
  transition: background 0.15s ease, border-color 0.15s ease;
}

.btn-primary {
  background: var(--signal);
  color: #1a0f05;
  font-weight: 600;
}

.btn-primary:hover {
  background: #ffa15e;
}

.btn-ghost {
  border-color: var(--rule);
  color: var(--ink);
}

.btn-ghost:hover {
  border-color: var(--signal-dim);
}

/* ---------- Hero ---------- */

.hero {
  position: relative;
  padding-block: clamp(3.5rem, 8vw, 6.5rem) clamp(3rem, 6vw, 5rem);
  border-bottom: 1px solid var(--rule);
}

.hero .wrap {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(280px, 0.95fr);
  align-items: center;
  gap: clamp(2rem, 5vw, 4rem);
}

.hero h1 {
  font-size: clamp(2.3rem, 5vw, 3.5rem);
  line-height: 1.08;
  margin-block: 0.6rem 1.1rem;
}

.hero p.lede {
  color: var(--muted);
  font-size: 1.08rem;
  max-width: 42ch;
  margin: 0 0 1.9rem;
}

.hero .cta-row {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  flex-wrap: wrap;
}

.hero .cta-row .text-link {
  font-family: var(--font-mono);
  font-size: 0.88rem;
  color: var(--muted);
  text-decoration: none;
  border-bottom: 1px solid var(--rule);
}

.hero .cta-row .text-link:hover {
  color: var(--ink);
  border-color: var(--muted);
}

.hero-figure {
  position: relative;
  background: var(--panel);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 1rem;
}

.hero-figure canvas {
  width: 100%;
  height: auto;
  border-radius: 6px;
}

.hero-figure .caption {
  display: flex;
  justify-content: space-between;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--muted);
  margin-top: 0.6rem;
  font-variant-numeric: tabular-nums;
}

.hero-figure .caption .signal-dot {
  color: var(--signal);
}

/* ---------- Section shell ---------- */

section {
  padding-block: clamp(3rem, 6vw, 4.5rem);
}

/* .topbar is sticky (~76px tall); without this, jumping to #module or
   #aufbau from the nav lands the section flush under the viewport top,
   i.e. hidden behind the header instead of visible below it. */
section[id] {
  scroll-margin-top: 5rem;
}

.section-head {
  max-width: 56ch;
  margin-bottom: 2.5rem;
}

.section-head h2 {
  font-size: clamp(1.6rem, 3vw, 2.1rem);
  margin-top: 0.5rem;
}

.section-head p {
  color: var(--muted);
  margin-top: 0.75rem;
}

/* ---------- Tool cards ---------- */

.tools {
  border-bottom: 1px solid var(--rule);
  background: color-mix(in srgb, var(--panel) 35%, transparent);
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.25rem;
}

@media (max-width: 720px) {
  .card-grid {
    grid-template-columns: 1fr;
  }
  .hero .wrap {
    grid-template-columns: 1fr;
  }
  .hero-figure {
    order: -1;
  }
}

.card {
  background: var(--panel);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.18s ease, background 0.18s ease;
}

.card:hover {
  border-color: var(--signal-dim);
  background: var(--panel-raised);
}

.card .diagram {
  background: var(--canvas);
  border: 1px solid var(--rule);
  border-radius: 6px;
  aspect-ratio: 16 / 9;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem;
}

.card .diagram svg {
  width: 100%;
  height: 100%;
}

.card h3 {
  font-size: 1.2rem;
}

.card p {
  color: var(--muted);
  font-size: 0.95rem;
  margin: 0;
  flex-grow: 1;
}

.card .path {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--signal);
  font-variant-numeric: tabular-nums;
}

/* card-specific diagram motion */
.card .diagram .moving {
  transition: transform 0.5s ease, stroke-dashoffset 0.6s ease;
  transform-origin: center;
}

.card:hover #knn-ring {
  transform: scale(1.12);
}

.card:hover #perceptron-line {
  transform: rotate(-6deg);
}

.card:hover #gd-ball {
  transform: translate(35px, 10px);
}

.card:hover #nn-pulse {
  stroke-dashoffset: 0;
}

/* ---------- About ---------- */

.about .wrap {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(220px, 0.5fr);
  gap: clamp(2rem, 5vw, 4rem);
  align-items: start;
}

.about p {
  color: var(--muted);
}

.about p + p {
  margin-top: 1rem;
}

/* Plain ruled list rather than a boxed "stats" card: it is a stack
   listing, not a metric. */
.about .stat-block {
  border-top: 1px solid var(--rule);
  font-family: var(--font-mono);
  font-size: 0.85rem;
}

.about .stat-block dl {
  margin: 0;
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0;
}

.about .stat-block dt,
.about .stat-block dd {
  padding-block: 0.6rem;
  border-bottom: 1px solid var(--rule);
}

.about .stat-block dt {
  color: var(--muted);
}

.about .stat-block dd {
  margin: 0;
  text-align: right;
  font-variant-numeric: tabular-nums;
  color: var(--contrast);
}

@media (max-width: 720px) {
  .about .wrap {
    grid-template-columns: 1fr;
  }
}

/* ---------- Footer ---------- */

footer {
  border-top: 1px solid var(--rule);
  padding-block: 2.5rem;
}

footer .wrap {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 1rem;
  font-size: 0.88rem;
  color: var(--muted);
}

footer a {
  color: var(--muted);
  text-decoration: underline;
  text-decoration-color: var(--rule);
  text-underline-offset: 3px;
}

footer a:hover {
  color: var(--ink);
  text-decoration-color: var(--muted);
}

footer .links {
  display: flex;
  gap: 1.25rem;
  flex-wrap: wrap;
}

@media (prefers-reduced-motion: reduce) {
  * {
    transition-duration: 0.001ms !important;
    animation-duration: 0.001ms !important;
  }
}