/* ============================================================
   01Academy · Header & Navigation
   Vivid+Co Design System — Prismatic Light Through Obsidian
   ============================================================ */

.header {
  position: sticky;
  top: 0;
  z-index: var(--z-header);
  background: rgba(16, 16, 16, 0.82);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid transparent;
  transition:
    height var(--dur) var(--ease-vivid),
    border-color var(--dur) var(--ease-vivid),
    background-color var(--dur) var(--ease-vivid);
}

.header.is-stuck {
  border-bottom-color: var(--color-ash-border);
  background: rgba(16, 16, 16, 0.94);
}

.header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-40);
  height: var(--header-h);
  transition: height var(--dur) var(--ease-vivid);
}

.header.is-stuck .header__inner {
  height: var(--header-h-shrunk);
}

/* --- Read Progress Indicator --- */
.header__progress {
  position: absolute;
  left: 0;
  bottom: -1px;
  height: 1px;
  width: 100%;
  transform: scaleX(var(--progress, 0));
  transform-origin: left;
  background: var(--color-bone-white);
  transition: transform 0.1s linear;
  pointer-events: none;
}

/* --- Wordmark / Logo --- */
.logo {
  display: inline-flex;
  align-items: baseline;
  font-family: var(--font-neue-montreal);
  font-weight: var(--font-weight-regular);
  font-size: 20px;
  letter-spacing: -0.02em;
  color: var(--color-bone-white);
  flex-shrink: 0;
  text-decoration: none;
}

.logo span {
  color: var(--color-bone-white);
  opacity: 0.9;
}

/* --- Ghost Navigation Links ---
   Role: Primary navigation item
   Transparent fill, #fffdf9 text, 0px radius, uppercase Neue Montreal 14–15px.
   No underline, no border — letterforms alone carry identification.
   Hover transitions color only via 0.5s cubic-bezier(0.52,0.01,0,1).
   ------------------------------------------------------------ */
.nav {
  display: flex;
  align-items: center;
  gap: clamp(20px, 2.5vw, 36px);
}

.nav__link {
  position: relative;
  font-family: var(--font-neue-montreal);
  font-size: 14px;
  font-weight: var(--font-weight-regular);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--color-bone-white);
  padding: 0;
  border-radius: 0px;
  background: transparent;
  text-decoration: none;
  transition: color var(--dur) var(--ease-vivid);
  white-space: nowrap;
}

.nav__link:hover {
  color: var(--color-fog-blue);
}

.nav__link.is-active {
  color: var(--color-bone-white);
}

.nav__link::after {
  display: none;
}

/* --- Outlined Contact Button ---
   Role: Sole outlined call-to-action in the nav
   Transparent fill, 1px solid #fffdf9 border, 5px radius, padding 9px 15px, uppercase 14px #fffdf9 text.
   The only bordered element in the header.
   ------------------------------------------------------------ */
.header__cta {
  flex-shrink: 0;
  background: transparent;
  border: 1px solid var(--color-bone-white);
  border-radius: var(--radius-nav);
  padding: 9px 15px;
  font-family: var(--font-neue-montreal);
  font-weight: var(--font-weight-regular);
  font-size: 14px;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  color: var(--color-bone-white);
  transition:
    background-color var(--dur) var(--ease-vivid),
    color var(--dur) var(--ease-vivid);
}

.header__cta:hover {
  background: var(--color-bone-white);
  color: var(--color-obsidian);
}

/* --- Burger Button --- */
.burger {
  display: none;
  width: 42px;
  height: 42px;
  border-radius: var(--radius-nav);
  border: 1px solid var(--color-ash-border);
  background: transparent;
  place-items: center;
  flex-shrink: 0;
  cursor: pointer;
  transition: border-color var(--dur) var(--ease-vivid);
}

.burger:hover {
  border-color: var(--color-bone-white);
}

.burger__box {
  width: 18px;
  height: 12px;
  position: relative;
}

.burger__box span {
  position: absolute;
  left: 0;
  width: 100%;
  height: 1.5px;
  border-radius: 0;
  background: var(--color-bone-white);
  transition: transform var(--dur) var(--ease-vivid), opacity var(--dur-fast) var(--ease-vivid);
}

.burger__box span:nth-child(1) { top: 0; }
.burger__box span:nth-child(2) { top: 50%; margin-top: -0.75px; }
.burger__box span:nth-child(3) { bottom: 0; }

.burger[aria-expanded="true"] .burger__box span:nth-child(1) {
  transform: translateY(5.25px) rotate(45deg);
}
.burger[aria-expanded="true"] .burger__box span:nth-child(2) {
  opacity: 0;
}
.burger[aria-expanded="true"] .burger__box span:nth-child(3) {
  transform: translateY(-5.25px) rotate(-45deg);
}

/* --- Mobile Drawer --- */
.drawer {
  position: fixed;
  inset: 0;
  z-index: var(--z-drawer);
  background: var(--color-obsidian);
  padding: calc(var(--header-h) + 24px) var(--gutter) 40px;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-16);
  overflow-y: auto;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition:
    opacity var(--dur) var(--ease-vivid),
    transform var(--dur) var(--ease-vivid),
    visibility var(--dur) var(--ease-vivid);
}

.drawer.is-open {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

body.is-locked .header {
  background: var(--color-obsidian);
}

.drawer__link {
  font-family: var(--font-neue-montreal);
  font-size: 22px;
  font-weight: var(--font-weight-regular);
  letter-spacing: -0.01em;
  text-transform: uppercase;
  color: var(--color-bone-white);
  padding-block: 16px;
  border-bottom: 1px solid var(--color-ash-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  text-decoration: none;
  transition: color var(--dur) var(--ease-vivid);
}

.drawer__link:hover,
.drawer__link.is-active {
  color: var(--color-fog-blue);
}

.drawer__link svg {
  width: 16px;
  height: 16px;
  color: var(--color-bone-white);
  opacity: 0.6;
}

.drawer__foot {
  margin-top: auto;
  padding-top: var(--spacing-40);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-16);
}

.drawer__contact {
  font-size: var(--text-caption);
  color: var(--color-fog-blue);
  text-align: center;
}

@media (max-width: 980px) {
  .nav { display: none; }
  .burger { display: grid; }
  .header__cta { display: none; }
}

@media (min-width: 981px) {
  .drawer { display: none; }
}

/* --- Sticky CTA for Mobile --- */
.sticky-cta {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: var(--z-sticky);
  padding: 12px var(--gutter) calc(12px + env(safe-area-inset-bottom));
  background: rgba(16, 16, 16, 0.95);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-top: 1px solid var(--color-ash-border);
  transform: translateY(110%);
  transition: transform var(--dur) var(--ease-vivid);
  display: none;
}

.sticky-cta.is-visible {
  transform: translateY(0);
}

@media (max-width: 980px) {
  .sticky-cta { display: block; }
}

/* --- To Top Button --- */
.to-top {
  position: fixed;
  right: 28px;
  bottom: 28px;
  z-index: var(--z-sticky);
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: #15181c;
  color: var(--color-bone-white);
  border: 1px solid var(--color-ash-border);
  display: grid;
  place-items: center;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition:
    opacity var(--dur) var(--ease-vivid),
    transform var(--dur) var(--ease-vivid),
    visibility var(--dur) var(--ease-vivid),
    border-color var(--dur) var(--ease-vivid),
    background-color var(--dur) var(--ease-vivid);
}

.to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.to-top:hover {
  background: var(--color-bone-white);
  color: var(--color-obsidian);
  border-color: var(--color-bone-white);
}

.to-top svg {
  width: 18px;
  height: 18px;
}

@media (max-width: 980px) {
  .to-top { display: none; }
}

/* --- Skip Link --- */
.skip-link {
  position: absolute;
  left: 50%;
  top: 8px;
  transform: translate(-50%, -200%);
  z-index: var(--z-top);
  background: var(--color-bone-white);
  color: var(--color-obsidian);
  padding: 10px 20px;
  border-radius: var(--radius-nav);
  font-size: 14px;
  transition: transform var(--dur) var(--ease-vivid);
  text-decoration: none;
}

.skip-link:focus {
  transform: translate(-50%, 0);
}