/* =========================================================================
   multi — landing page styles
   Design tokens mirror STYLEGUIDE.md. Change a value once, here.
   ========================================================================= */

/* Self-hosted Inter (no third-party font CDN → no data leaves the server) */
@font-face {
  font-family: "Inter";
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url("/fonts/inter-400.woff2") format("woff2");
}
@font-face {
  font-family: "Inter";
  font-style: normal;
  font-weight: 500;
  font-display: swap;
  src: url("/fonts/inter-500.woff2") format("woff2");
}
@font-face {
  font-family: "Inter";
  font-style: normal;
  font-weight: 600;
  font-display: swap;
  src: url("/fonts/inter-600.woff2") format("woff2");
}
@font-face {
  font-family: "Inter";
  font-style: normal;
  font-weight: 700;
  font-display: swap;
  src: url("/fonts/inter-700.woff2") format("woff2");
}

:root {
  /* Brand */
  --multi-indigo: #171754;
  --multi-indigo-700: #232374;
  --multi-indigo-600: #2e2e8f;
  --multi-mint: #1de8a4;
  --multi-mint-600: #12c78a;
  --multi-slate: #5c5c6e;
  --multi-purple-100: rgba(186, 186, 255, 0.55);

  /* Call to action */
  --multi-blue: #344fff;
  --multi-blue-600: #1f36e0;

  /* Neutrals & surfaces */
  --multi-bg: #f7f6fb;
  --multi-offwhite: #f7f6f2;
  --multi-surface: #ffffff;
  --multi-surface-2: #f3f2f9;
  --multi-border: #e6e5ef;
  --multi-border-strong: #d6d5e4;
  --multi-text: #26263a;
  --multi-text-muted: #6b6b7b;
  --multi-text-on-dark: #f5f4ef;

  /* Gradient */
  --multi-hero-gradient: linear-gradient(to bottom, #f7f6f2, #a3a7e3);

  /* Radius */
  --multi-radius-sm: 8px;
  --multi-radius: 12px;
  --multi-radius-lg: 18px;
  --multi-radius-pill: 999px;

  /* Elevation */
  --multi-shadow-sm: 0 1px 2px rgba(23, 23, 84, 0.06), 0 1px 3px rgba(23, 23, 84, 0.08);
  --multi-shadow: 0 6px 20px rgba(23, 23, 84, 0.1);
  --multi-shadow-lg: 0 12px 32px rgba(23, 23, 84, 0.16);
  --multi-shadow-xl: 0 30px 70px rgba(23, 23, 84, 0.22);
  --multi-ring: 0 0 0 3px rgba(52, 79, 255, 0.28);

  /* Motion */
  --multi-transition: 160ms ease;
  --multi-transition-slow: 320ms cubic-bezier(0.22, 1, 0.36, 1);

  /* Spacing scale (4-based) */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 24px;
  --space-6: 32px;
  --space-7: 48px;
  --space-8: 64px;
  --space-9: 96px;

  /* Layout */
  --container: 1120px;
  --container-narrow: 760px;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 96px;
  -webkit-text-size-adjust: 100%;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}

body {
  margin: 0;
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    Helvetica, Arial, sans-serif;
  font-weight: 400;
  color: var(--multi-text);
  background: var(--multi-surface);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

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

a {
  color: var(--multi-blue-600);
  text-decoration: none;
  transition: color var(--multi-transition);
}

a:hover {
  color: var(--multi-blue);
}

h1,
h2,
h3 {
  color: var(--multi-indigo);
  font-weight: 700;
  letter-spacing: -0.01em;
  line-height: 1.15;
  margin: 0;
}

p {
  margin: 0;
}

:focus-visible {
  outline: none;
  box-shadow: var(--multi-ring);
  border-radius: var(--multi-radius-sm);
}

/* ---------------------------------------------------------------- layout */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--space-5);
}

.section {
  padding-block: var(--space-9);
}

.section__head {
  max-width: var(--container-narrow);
  margin-inline: auto;
  text-align: center;
  margin-bottom: var(--space-8);
}

.section__eyebrow {
  display: inline-block;
  font-size: 0.8125rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--multi-blue-600);
  margin-bottom: var(--space-3);
}

.section__title {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
}

.section__lead {
  margin-top: var(--space-4);
  font-size: 1.125rem;
  color: var(--multi-text-muted);
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--multi-indigo);
  color: var(--multi-text-on-dark);
  padding: var(--space-3) var(--space-4);
  border-radius: var(--multi-radius-sm);
  z-index: 100;
}

.skip-link:focus {
  left: var(--space-4);
  top: var(--space-4);
}

/* --------------------------------------------------------------- buttons */
.btn {
  --btn-bg: var(--multi-blue);
  --btn-bg-hover: var(--multi-blue-600);
  --btn-fg: var(--multi-text-on-dark);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  font-family: inherit;
  font-weight: 600;
  font-size: 1rem;
  line-height: 1;
  padding: 0.875rem 1.5rem;
  border: 1px solid transparent;
  border-radius: var(--multi-radius-sm);
  background: var(--btn-bg);
  color: var(--btn-fg);
  cursor: pointer;
  white-space: nowrap;
  transition: background var(--multi-transition), transform var(--multi-transition),
    box-shadow var(--multi-transition), color var(--multi-transition),
    border-color var(--multi-transition);
}

.btn:hover {
  background: var(--btn-bg-hover);
  color: var(--btn-fg);
  transform: translateY(-1px);
  box-shadow: var(--multi-shadow);
}

.btn:active {
  transform: translateY(1px);
  box-shadow: var(--multi-shadow-sm);
}

.btn--lg {
  padding: 1.05rem 2rem;
  font-size: 1.0625rem;
}

.btn--ghost {
  --btn-bg: transparent;
  --btn-bg-hover: rgba(23, 23, 84, 0.06);
  --btn-fg: var(--multi-indigo);
  border-color: var(--multi-border-strong);
}

.btn--ghost:hover {
  box-shadow: none;
}

.btn--block {
  width: 100%;
}

.btn__icon {
  width: 18px;
  height: 18px;
  flex: none;
}

/* ------------------------------------------------------------------- hero */
.hero {
  position: relative;
  background: var(--multi-hero-gradient);
  padding-bottom: var(--space-9);
  overflow: hidden;
}

/* Invisible topbar — logical header, visually part of the hero */
.masthead {
  position: relative;
  z-index: 2;
}

.masthead__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-5);
  padding-block: var(--space-5);
}

.brand {
  display: inline-flex;
  align-items: center;
  flex: none;
}

.brand img {
  height: 42px;
  width: auto;
}

.nav {
  display: flex;
  align-items: center;
  gap: var(--space-6);
}

.nav__link {
  color: var(--multi-indigo);
  font-weight: 600;
  font-size: 0.9375rem;
  position: relative;
  padding-block: var(--space-1);
}

.nav__link::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -2px;
  width: 100%;
  height: 2px;
  background: var(--multi-blue);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--multi-transition-slow);
}

.nav__link:hover {
  color: var(--multi-indigo);
}

.nav__link:hover::after {
  transform: scaleX(1);
}

.masthead .btn {
  flex: none;
}

/* On desktop the CTA is the standalone right-aligned button. The copy inside
   the nav exists only for the mobile dropdown, so hide it here. */
.nav .btn {
  display: none;
}

/* mobile nav toggle */
.nav-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  padding: 0;
  border: 1px solid var(--multi-border-strong);
  border-radius: var(--multi-radius-sm);
  background: rgba(255, 255, 255, 0.5);
  color: var(--multi-indigo);
  cursor: pointer;
}

.hero__content {
  text-align: center;
  max-width: 820px;
  margin: var(--space-8) auto var(--space-7);
}

.hero__title {
  font-size: clamp(2.25rem, 6vw, 3.75rem);
  letter-spacing: -0.02em;
}

.hero__subtitle {
  margin-top: var(--space-5);
  font-size: clamp(1.0625rem, 2.5vw, 1.25rem);
  color: var(--multi-text-muted);
  max-width: 620px;
  margin-inline: auto;
}

/* Video / screencast placeholder */
.hero__media {
  max-width: 960px;
  margin: 0 auto var(--space-7);
}

.media-frame {
  position: relative;
  aspect-ratio: 16 / 9;
  border-radius: var(--multi-radius-lg);
  overflow: hidden;
  background: var(--multi-surface);
  box-shadow: var(--multi-shadow-xl);
  border: 1px solid rgba(255, 255, 255, 0.6);
  transition: transform var(--multi-transition-slow), box-shadow var(--multi-transition-slow);
}

.media-frame:hover {
  transform: translateY(-4px);
}

.media-frame img,
.media-frame video {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.hero__cta {
  text-align: center;
}

/* --------------------------------------------------------------- features */
.features {
  background: var(--multi-surface);
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-6);
}

.feature-card {
  background: var(--multi-surface);
  border: 1px solid var(--multi-border);
  border-radius: var(--multi-radius-lg);
  padding: var(--space-6);
  box-shadow: var(--multi-shadow-sm);
  transition: transform var(--multi-transition-slow), box-shadow var(--multi-transition-slow),
    border-color var(--multi-transition-slow);
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--multi-shadow);
  border-color: var(--multi-border-strong);
}

.feature-card__media {
  border-radius: var(--multi-radius);
  overflow: hidden;
  background: var(--multi-surface-2);
  margin-bottom: var(--space-5);
  aspect-ratio: 4 / 3;
}

.feature-card__media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.feature-card__title {
  font-size: 1.25rem;
  margin-bottom: var(--space-3);
}

.feature-card__text {
  color: var(--multi-text-muted);
  font-size: 0.9875rem;
}

/* --------------------------------------------------------------- research */
.research {
  background: var(--multi-bg);
}

/* ------------------------------------------------------- open source */
.open-source {
  background: var(--multi-surface);
}

.open-source__actions {
  display: flex;
  justify-content: center;
}

.research__grid {
  display: grid;
  grid-template-columns: 1fr auto auto;
  gap: var(--space-7);
  align-items: center;
}

.research__text {
  max-width: 460px;
}

.research__text .section__title {
  text-align: left;
  font-size: clamp(1.5rem, 3vw, 2rem);
}

.research__text p {
  margin-top: var(--space-4);
  color: var(--multi-text-muted);
  font-size: 1.0625rem;
}

/* Symbolized paper: a card that looks like a page from the paper */
.paper {
  width: 284px;
  aspect-ratio: 1 / 1.131; /* A4 sheet, 20% shorter */
  background: #fbfaf7;
  border: 1px solid var(--multi-border-strong);
  border-radius: var(--multi-radius);
  box-shadow: var(--multi-shadow-lg);
  padding: 24px 24px 28px;
  overflow: hidden;
  position: relative;
  transform: rotate(-1.5deg);
  transition: transform var(--multi-transition-slow), box-shadow var(--multi-transition-slow);
}

.paper:hover {
  transform: rotate(0deg) translateY(-4px);
  box-shadow: var(--multi-shadow-xl);
}

.paper__title {
  font-size: 0.9375rem;
  line-height: 1.3;
  font-weight: 700;
  color: var(--multi-indigo);
  letter-spacing: -0.01em;
  text-align: center;
}

.paper__authors {
  margin-top: 10px;
  font-size: 0.5rem;
  text-align: center;
  color: var(--multi-slate);
  letter-spacing: 0.02em;
}

.paper__cols {
  margin-top: 14px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  height: 158px;
  overflow: hidden;
}

/* miniature "text lines" */
.paper__lines {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.paper__lines span {
  display: block;
  height: 3px;
  border-radius: 2px;
  background: #d9d7cf;
}

.paper__lines span:nth-child(4n) {
  width: 70%;
}
.paper__lines span:nth-child(3n) {
  width: 92%;
}

/* blank line separating "paragraphs" */
.paper__lines span.paper__gap {
  background: transparent;
  height: 6px;
}

.research__actions {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  min-width: 220px;
}

.research__actions .btn {
  justify-content: flex-start;
  text-align: left;
}

.research__actions small {
  display: block;
  font-weight: 400;
  font-size: 0.75rem;
  opacity: 0.75;
}

.link-card {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

/* ---------------------------------------------------------------- footer */
.footer {
  background: var(--multi-indigo);
  color: var(--multi-text-on-dark);
  padding-block: var(--space-8) var(--space-6);
}

.footer__grid {
  display: grid;
  grid-template-columns: 1.6fr auto var(--space-9);
  gap: var(--space-7);
  align-items: start;
}

.footer__nav {
  display: flex;
  gap: var(--space-9);
}

.footer__brand img {
  height: 30px;
  margin-bottom: var(--space-4);
}

.footer__desc {
  color: rgba(245, 244, 239, 0.72);
  max-width: 42ch;
  font-size: 0.9375rem;
}

.footer__links {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.footer__links-title {
  font-size: 0.8125rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: rgba(245, 244, 239, 0.55);
  margin-bottom: var(--space-2);
}

.footer__links a {
  color: rgba(245, 244, 239, 0.85);
  font-size: 0.9375rem;
  width: fit-content;
}

.footer__links a:hover {
  color: var(--multi-mint);
}

.footer__bottom {
  margin-top: var(--space-7);
  padding-top: var(--space-5);
  border-top: 1px solid rgba(245, 244, 239, 0.14);
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
  justify-content: space-between;
  align-items: center;
  color: rgba(245, 244, 239, 0.6);
  font-size: 0.875rem;
}

/* --------------------------------------------------------- content pages */
.page-hero {
  background: var(--multi-hero-gradient);
  padding-block: var(--space-6) var(--space-9);
}

.page-hero .hero__content {
  margin-block: var(--space-8) var(--space-6);
}

.page-hero .hero__subtitle {
  color: var(--multi-text);
}

.page-hero__title {
  font-size: clamp(2rem, 5vw, 3rem);
}

/* Airy nav-bar variant: gradient masthead only, no hero copy */
.page-hero--bar {
  padding-block: var(--space-4);
  background: linear-gradient(to bottom, #f7f6f2, #d3d5f3);
}

.prose {
  max-width: var(--container-narrow);
  margin-inline: auto;
}

/* Page header sitting inline with the prose, left aligned */
.page-head {
  margin-bottom: var(--space-7);
}

.page-head__title {
  font-size: clamp(2rem, 5vw, 3rem);
  letter-spacing: -0.02em;
}

.page-head__subtitle {
  margin-top: var(--space-4);
  font-size: clamp(1.0625rem, 2.5vw, 1.25rem);
  color: var(--multi-text-muted);
  max-width: 60ch;
}

.prose h2 {
  font-size: 1.5rem;
  margin-top: var(--space-8);
  margin-bottom: var(--space-3);
}

.prose h3 {
  font-size: 1.15rem;
  margin-top: var(--space-6);
  margin-bottom: var(--space-2);
}

.prose p,
.prose li {
  color: var(--multi-text);
  font-size: 1.0625rem;
}

.prose p + p {
  margin-top: var(--space-4);
}

.prose ul {
  margin-block: var(--space-3);
  padding-left: 1.25rem;
}

.prose li {
  margin-block: var(--space-2);
}

.prose a {
  text-decoration: underline;
  text-underline-offset: 2px;
}

.prose .muted {
  color: var(--multi-text-muted);
  font-size: 0.9375rem;
}

.callout {
  background: var(--multi-surface-2);
  border: 1px solid var(--multi-border);
  border-left: 3px solid var(--multi-blue);
  border-radius: var(--multi-radius);
  padding: var(--space-4) var(--space-5);
  margin-block: var(--space-5);
}

.callout p {
  font-size: 0.9375rem;
  color: var(--multi-text-muted);
}

.definition-table {
  width: 100%;
  border-collapse: collapse;
  margin-block: var(--space-4);
  font-size: 0.9375rem;
}

.definition-table th,
.definition-table td {
  text-align: left;
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--multi-border);
  vertical-align: top;
}

.definition-table th {
  color: var(--multi-indigo);
  width: 34%;
  font-weight: 600;
}

/* --------------------------------------------------------- scroll reveal */
/* Only hide-then-reveal when JS is available (html.js). Without JS every
   .reveal stays fully visible, so crawlers and no-JS users see all content. */
.js .reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.7s cubic-bezier(0.22, 1, 0.36, 1),
    transform 0.7s cubic-bezier(0.22, 1, 0.36, 1);
  will-change: opacity, transform;
}

.js .reveal.is-visible {
  opacity: 1;
  transform: none;
}

.reveal--d1 {
  transition-delay: 0.08s;
}
.reveal--d2 {
  transition-delay: 0.16s;
}

@media (prefers-reduced-motion: reduce) {
  .js .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }
  .media-frame:hover,
  .feature-card:hover,
  .paper:hover {
    transform: none;
  }
}

/* ---------------------------------------------------------- responsive */
@media (max-width: 900px) {
  .research__grid {
    grid-template-columns: 1fr;
    justify-items: center;
    text-align: center;
    gap: var(--space-6);
  }
  .research__text {
    max-width: 560px;
  }
  .research__text .section__title {
    text-align: center;
  }
  .research__actions {
    width: 100%;
    max-width: 320px;
  }
}

@media (max-width: 760px) {
  .section {
    padding-block: var(--space-8);
  }

  .nav-toggle {
    display: inline-flex;
  }

  .nav {
    position: absolute;
    top: calc(100% + 4px);
    right: var(--space-5);
    left: var(--space-5);
    flex-direction: column;
    align-items: stretch;
    gap: var(--space-2);
    background: var(--multi-surface);
    border: 1px solid var(--multi-border);
    border-radius: var(--multi-radius);
    box-shadow: var(--multi-shadow-lg);
    padding: var(--space-4);
    z-index: 20;
    opacity: 0;
    transform: translateY(-8px);
    pointer-events: none;
    transition: opacity var(--multi-transition), transform var(--multi-transition);
  }

  .nav.is-open {
    opacity: 1;
    transform: none;
    pointer-events: auto;
  }

  .nav__link {
    padding: var(--space-3);
    border-radius: var(--multi-radius-sm);
  }

  .nav__link::after {
    display: none;
  }

  .nav .btn {
    display: inline-flex;
    margin-top: var(--space-1);
  }

  /* keep the header CTA button hidden on mobile — it lives in the menu */
  .masthead__inner > .btn {
    display: none;
  }

  .feature-grid {
    grid-template-columns: 1fr;
  }

  .footer__grid {
    grid-template-columns: 1fr;
    gap: var(--space-6);
  }
}