/* =========================================
   AgileAI Public Surface — Institutional CSS v11.4

   Safe Structural Upgrade
   - No layout changes
   - No typography changes
   - No nav logic changes
   - Adds controlled hamburger visibility
   - Mobile hamburger styled intentionally
========================================= */


/* =========================
   ROOT VARIABLES
========================= */

:root {
  --text-primary: #111111;
  --text-secondary: #555555;
  --border-subtle: #e6e6e6;
  --background: #ffffff;
  --surface-muted: #f6f6f6;
  --surface-elevated: rgba(255,255,255,0.94);

  --max-width: 720px;
  --header-height: 80px;

  --transition-speed: 180ms;
  --motion-standard: cubic-bezier(.4,0,.2,1);

  --link-color: #2e5c7a;
  --link-hover: #1f3f56;
}

:root[data-theme="dark"] {
  --text-primary: #f2f2f2;
  --text-secondary: #b5b5b5;
  --border-subtle: #2a2a2a;
  --background: #0f1115;
  --surface-muted: #151821;
  --surface-elevated: rgba(27,31,38,0.94);

  --link-color: #7fb3d5;
  --link-hover: #a8d0ea;
}


/* =========================
   BASE
========================= */

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--background);
  color: var(--text-primary);
  font-family: Georgia, "Times New Roman", serif;
  font-size: 18px;
  line-height: 1.72;
  transition:
    background var(--transition-speed),
    color var(--transition-speed);
}

body.nav-open {
  overflow: hidden;
}


/* =========================
   HEADER
========================= */

#header { width: 100%; }

.site-header {
  width: 100%;
  height: var(--header-height);
  border-bottom: 1px solid var(--border-subtle);
  background: var(--background);

  position: fixed;
  top: 0;
  left: 0;
  right: 0;

  z-index: 5000;
  display: flex;
  align-items: center;

  box-shadow: 0 4px 12px rgba(0,0,0,0.06);
}

.header-inner {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 32px;

  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand a {
  text-decoration: none;
  color: var(--text-primary);
  font-size: 1rem;
  font-weight: 400;
}


/* =========================
   NAVIGATION
========================= */

.main-nav { position: relative; }

.nav-tree {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  gap: 22px;
  align-items: center;
}

.nav-item { position: relative; }

.nav-item > a,
.nav-toggle {
  background: none;
  border: none;
  font-family: inherit;
  font-size: 0.87rem;
  font-weight: 400;
  letter-spacing: 0.15px;
  color: var(--text-primary);
  cursor: pointer;
  padding: 0;

  display: inline-flex;
  align-items: center;
  gap: 6px;

  transition: opacity 140ms ease;
}

.nav-item > a:hover,
.nav-toggle:hover {
  opacity: 0.8;
}

.nav-toggle::after {
  content: "▾";
  font-size: 0.7rem;
  transition: transform 180ms var(--motion-standard);
}

.nav-item.is-open > .nav-toggle::after {
  transform: rotate(180deg);
}

.sub-menu {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 6px;
}


/* =========================
   DESKTOP NAV
========================= */

@media (min-width: 769px) {

  /* Hide hamburger completely on desktop */
  .nav-hamburger {
    display: none;
  }

  .nav-item > .sub-menu {
    position: absolute;
    right: 0;
    top: 100%;

    background: var(--surface-elevated);
    border: 1px solid var(--border-subtle);
    border-radius: 4px;

    padding: 10px 14px;
    min-width: 240px;

    box-shadow: 0 10px 28px rgba(0,0,0,0.06);

    backdrop-filter: blur(6px);
    -webkit-backdrop-filter: blur(6px);

    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transform: translateY(4px);

    transition:
      opacity 160ms ease,
      transform 200ms var(--motion-standard),
      visibility 0s linear 160ms;
  }

  .nav-item:hover > .sub-menu {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
    transform: translateY(0);
  }

  .sub-menu .sub-menu {
    position: static;
    background: transparent;
    border: none;
    box-shadow: none;
    padding-left: 14px;
    margin-top: 6px;
    border-left: 1px solid var(--border-subtle);
  }
}


/* =========================
   MOBILE NAV
========================= */

@media (max-width: 768px) {

  .header-inner { padding: 0 20px; }

  /* Hamburger styling (only mobile) */
  .nav-hamburger {
    display: flex;
    flex-direction: column;
    justify-content: center;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
  }

  .nav-hamburger span {
    width: 22px;
    height: 2px;
    background: var(--text-primary);
    display: block;
  }

  .main-nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;

    background: var(--background);
    border-bottom: 1px solid var(--border-subtle);

    max-height: 0;
    overflow: hidden;

    transition: max-height 260ms var(--motion-standard);
  }

  body.nav-open .main-nav {
    max-height: calc(100vh - var(--header-height));
    overflow-y: auto;
  }

  .nav-tree {
    flex-direction: column;
    align-items: flex-start;
    gap: 18px;
    padding: 24px 20px;
  }

  .nav-item > .sub-menu {
    max-height: 0;
    overflow: hidden;
    padding-left: 14px;
    margin-top: 6px;
    opacity: 0;

    transition:
      max-height 260ms var(--motion-standard),
      opacity 180ms ease;
  }

  .nav-item.is-open > .sub-menu {
    max-height: 600px;
    opacity: 1;
  }
}


/* =========================
   LAYOUT
========================= */

main {
  max-width: var(--max-width);
  margin: 100px auto;
  padding: 0 32px;
  min-height: calc(100vh - 200px);
}


/* =========================
   TYPOGRAPHY
========================= */

h1 {
  font-size: 2.9rem;
  font-weight: 500;
  line-height: 1.18;
  letter-spacing: -0.4px;
  margin-bottom: 30px;
}

h2 {
  font-size: 1.85rem;
  font-weight: 500;
  line-height: 1.28;
  letter-spacing: -0.2px;
  margin-top: 76px;
  margin-bottom: 22px;
}

p {
  margin-top: 0;
  margin-bottom: 22px;
  max-width: 68ch;
}


/* =========================
   HERO RHYTHM
========================= */

main > section:first-of-type {
  margin-bottom: 60px;
}

main > section:first-of-type p:last-of-type {
  margin-bottom: 34px;
}


/* =========================
   LISTS
========================= */

main ul {
  margin-top: 18px;
  margin-bottom: 28px;
  padding-left: 22px;
}

main ul li {
  margin-bottom: 10px;
  line-height: 1.6;
}


/* =========================
   CTA
========================= */

.btn {
  display: inline-block;
  margin-top: 16px;
  padding: 10px 20px;
  border-radius: 4px;
  font-weight: 500;
  font-size: 0.92rem;
  letter-spacing: 0.2px;
  text-decoration: none;
  transition: opacity 160ms ease;
}

.btn.primary {
  background: var(--text-primary);
  color: var(--background);
}

.btn.secondary {
  background: transparent;
  border: 1px solid var(--border-subtle);
  color: var(--text-primary);
}

.btn:hover {
  opacity: 0.85;
}


/* =========================
   LINKS
========================= */

a {
  color: var(--link-color);
  text-decoration: none;
  transition: color 150ms ease;
}

a:hover {
  color: var(--link-hover);
  text-decoration: underline;
}

main a {
  text-decoration-thickness: 0.8px;
  text-underline-offset: 2px;
  font-weight: 500;
}


/* =========================
   FOOTER
========================= */

#footer { margin-top: 120px; }

.site-footer {
  border-top: 1px solid var(--border-subtle);
  padding: 48px 32px;
  background: var(--surface-muted);
}

.footer-inner {
  max-width: 720px;
  margin: 0 auto;
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
}