/* ============================================================
   01Academy · Header & Navigation
   Applied AI for Business — Off-white / Graphite / Lime
   ============================================================ */

.header {
  position: sticky;
  top: 0;
  z-index: var(--z-header);
  background: color-mix(in srgb, var(--surface) 82%, transparent);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid transparent;
  /* height тут не анимируем: высоту держит .header__inner, у самой шапки
     этого свойства нет. */
  transition:
    border-color var(--dur) var(--ease-vivid),
    background-color var(--dur) var(--ease-vivid);
}

.header.is-stuck {
  border-bottom-color: var(--line);
  background: color-mix(in srgb, var(--surface) 94%, transparent);
}

.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(--ink);
  transition: transform 0.1s linear;
  pointer-events: none;
}

/* --- Wordmark / Logo --- */
.logo {
  display: inline-flex;
  align-items: center;
  /* Сам лоскут — 24px по высоте, но цель клика должна быть не меньше 24px
     и на мобильном, где картинка сжимается до 20px. */
  min-height: 24px;
  flex-shrink: 0;
  text-decoration: none;
}

.logo__brand {
  display: block;
  width: clamp(116px, 10vw, 148px);
  height: auto;
  aspect-ratio: 520 / 160;
  color: var(--ink);
}

/* --- 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);
}

/* Три состояния должны отличаться: обычное — приглушённое,
   наведение — ярче, текущий раздел — ярче и с подчёркиванием.
   Вертикальный padding доводит цель клика до 24px (WCAG 2.5.8). */
.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(--ink-2);
  padding-block: 10px;
  border-radius: 0px;
  background: transparent;
  text-decoration: none;
  transition: color var(--dur) var(--ease-vivid);
  white-space: nowrap;
}

.nav__link:hover,
.nav__link:focus-visible {
  color: var(--ink);
}

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

/* Маркер текущего раздела */
.nav__link::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 4px;
  height: 1px;
  background: var(--ink);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--dur) var(--ease-vivid);
}

.nav__link.is-active::after {
  transform: scaleX(1);
}

/* --- 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(--ink);
  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(--ink);
  transition:
    background-color var(--dur) var(--ease-vivid),
    color var(--dur) var(--ease-vivid);
}

.header__cta:hover {
  background: var(--ink);
  color: var(--surface);
}

.header__actions {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
}

/* --- Language Switcher --- */
.lang-switch {
  display: inline-flex;
  align-items: center;
  background: color-mix(in srgb, var(--ink) 5%, transparent);
  border: 1px solid var(--line);
  border-radius: var(--radius-nav);
  padding: 3px;
  gap: 2px;
  flex-shrink: 0;
}

/* Кнопка была 34×20 — ниже минимальной цели 24×24 (WCAG 2.5.8).
   Поднимаем высоту, не трогая рисунок переключателя. */
.lang-switch__btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 34px;
  min-height: 24px;
  font-family: var(--font-neue-montreal);
  font-size: 12px;
  font-weight: 500;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--ink-2);
  background: transparent;
  border: none;
  border-radius: 4px;
  padding: 4px 8px;
  cursor: pointer;
  line-height: 1;
  transition:
    color var(--dur-fast) var(--ease-vivid),
    background-color var(--dur-fast) var(--ease-vivid);
}

.lang-switch__btn:hover {
  color: var(--ink);
}

.lang-switch__btn.is-active {
  color: var(--surface);
  background: var(--ink);
  font-weight: 700;
}

/* --- Burger Button --- */
.burger {
  display: none;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-nav);
  border: 1px solid var(--line);
  background: transparent;
  place-items: center;
  flex-shrink: 0;
  cursor: pointer;
  transition: border-color var(--dur) var(--ease-vivid);
}

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

.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(--ink);
  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(--surface);
  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(--surface);
}

.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(--ink-2);
  padding-block: 16px;
  border-bottom: 1px solid var(--line);
  display: flex;
  align-items: center;
  justify-content: space-between;
  text-decoration: none;
  transition: color var(--dur) var(--ease-vivid);
}

.drawer__link:hover,
.drawer__link:focus-visible,
.drawer__link.is-active {
  color: var(--ink);
}

.drawer__link.is-active svg {
  opacity: 1;
}

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

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

.drawer__lang {
  display: flex;
  align-items: center;
  justify-content: center;
  padding-block: var(--spacing-16);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  margin-block: var(--spacing-8);
}

.drawer__lang .lang-switch {
  padding: 4px;
  gap: 6px;
}

.drawer__lang .lang-switch__btn {
  font-size: 14px;
  padding: 8px 16px;
}

.drawer__contact {
  font-size: var(--text-caption);
  color: var(--ink-2);
  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: color-mix(in srgb, var(--surface) 95%, transparent);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-top: 1px solid var(--line);
  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: var(--surface-3);
  color: var(--ink);
  border: 1px solid var(--line);
  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(--ink);
  color: var(--surface);
  border-color: var(--ink);
}

.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(--ink);
  color: var(--surface);
  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);
}