/* ============================================================================
   tanro — Header, điều hướng, footer và các lưới bố cục
   ============================================================================ */

/* ---------------------------------------------------------------- Header - */
.site-header {
  position: sticky;
  top: 0;
  z-index: 90;
  background: var(--backdrop);
  backdrop-filter: saturate(160%) blur(20px);
  -webkit-backdrop-filter: saturate(160%) blur(20px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--t) var(--ease), background var(--t) var(--ease);
}
.site-header.is-stuck {
  border-bottom-color: var(--line);
  background: var(--bg);
}

.header-bar {
  height: var(--header-h);
  display: flex;
  align-items: center;
  gap: clamp(.75rem, 2vw, 2rem);
}

/* ---- Logo -------------------------------------------------------------- */
.brand {
  display: inline-flex;
  align-items: center;
  gap: .55rem;
  font-size: 1.18rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  white-space: nowrap;
  color: var(--ink);
}
.brand__mark {
  width: 26px; height: 26px;
  flex: none;
  color: var(--brand-lift);
}
.brand__tag {
  display: none;
  margin-left: .4rem;
  font-size: var(--fs-xs);
  font-weight: 600;
  letter-spacing: var(--tracking-caps);
  text-transform: uppercase;
  color: var(--ink-4);
}

/* ---- Điều hướng chính -------------------------------------------------- */
.nav { display: none; margin-inline: auto; }
.nav__list { display: flex; align-items: center; gap: .1rem; }

.nav__link {
  position: relative;
  display: block;
  padding: .55rem .72rem;
  border-radius: var(--r-sm);
  font-size: var(--fs-sm);
  font-weight: 600;
  color: var(--ink-2);
  white-space: nowrap;
  transition: color var(--t-fast) var(--ease);
}
.nav__link::after {
  content: "";
  position: absolute;
  left: .72rem; right: .72rem;
  bottom: 0;
  height: 2px;
  border-radius: 2px;
  background: var(--nav-accent, var(--brand-lift));
  transform: scaleX(0);
  transform-origin: center;
  transition: transform var(--t) var(--ease-out);
}
.nav__link:hover { color: var(--ink); }
.nav__link:hover::after { transform: scaleX(.55); }
.nav__link[aria-current="page"] {
  color: var(--nav-accent, var(--brand-lift));
}
.nav__link[aria-current="page"]::after { transform: scaleX(1); }

/* ---- Nhóm nút bên phải ------------------------------------------------- */
.header-actions {
  display: flex;
  align-items: center;
  gap: .5rem;
  margin-left: auto;
}

/* Nút tròn — mô-típ chính của header */
.icon-btn {
  display: grid;
  place-items: center;
  width: 42px; height: 42px;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--bg-elev);
  color: var(--ink-2);
  cursor: pointer;
  transition: background var(--t-fast) var(--ease), color var(--t-fast) var(--ease),
              border-color var(--t-fast) var(--ease), transform var(--t-fast) var(--ease);
}
.icon-btn:hover {
  background: var(--bg-raise);
  color: var(--ink);
  border-color: var(--line-strong);
  transform: translateY(-1px);
}

.icon-btn__kbd {
  display: none;
  padding: .1rem .3rem;
  border: 1px solid var(--line);
  border-radius: 5px;
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--ink-4);
}

/* Nút tìm kiếm giữ hình tròn, chỉ nới ra khi có chỗ */
.search-trigger span:not(.icon-btn__kbd) { display: none; }

/* ---- Chuyển ngôn ngữ --------------------------------------------------- */
.lang-switch {
  display: flex;
  align-items: center;
  padding: 3px;
  border: 1px solid var(--line);
  border-radius: var(--r-pill);
  background: var(--bg-elev);
}
.lang-switch a {
  padding: .28rem .6rem;
  border-radius: var(--r-pill);
  font-size: var(--fs-xs);
  font-weight: 700;
  color: var(--ink-3);
  transition: background var(--t-fast) var(--ease), color var(--t-fast) var(--ease);
}
.lang-switch a:hover { color: var(--ink); }
.lang-switch a.is-active {
  background: var(--brand);
  color: var(--brand-fg);
}

/* ---- Thanh tiến độ đọc bài -------------------------------------------- */
.read-progress {
  position: absolute;
  left: 0; bottom: -1px;
  height: 2px;
  width: 100%;
  transform: scaleX(var(--progress, 0));
  transform-origin: left;
  background: var(--brand);
  transition: transform .1s linear;
}

/* ---------------------------------------------------- Ngăn kéo di động - */
.drawer { position: fixed; inset: 0; z-index: 120; visibility: hidden; }
.drawer.is-open { visibility: visible; }

.drawer__scrim {
  position: absolute; inset: 0;
  background: rgba(0, 0, 0, .6);
  opacity: 0;
  transition: opacity var(--t) var(--ease);
}
.drawer.is-open .drawer__scrim { opacity: 1; }

.drawer__panel {
  position: absolute;
  inset-block: 0; right: 0;
  width: min(88vw, 360px);
  display: flex;
  flex-direction: column;
  padding: 1.1rem var(--pad-x) 2rem;
  background: var(--bg-elev);
  border-left: 1px solid var(--line);
  transform: translateX(100%);
  transition: transform var(--t-slow) var(--ease-out);
  overflow-y: auto;
  overscroll-behavior: contain;
}
.drawer.is-open .drawer__panel { transform: none; }

.drawer__head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-bottom: 1rem;
  margin-bottom: .5rem;
  border-bottom: 1px solid var(--line);
}

.drawer__list { display: flex; flex-direction: column; }
.drawer__list a {
  display: flex;
  align-items: center;
  gap: .8rem;
  padding: .85rem .25rem;
  border-bottom: 1px solid var(--line);
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: var(--tracking-tight);
  transition: padding-left var(--t) var(--ease-out), color var(--t-fast) var(--ease);
}
.drawer__list a::before {
  content: "";
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--nav-accent, var(--brand));
  transform: scale(.55);
  opacity: .45;
  transition: transform var(--t) var(--ease-out), opacity var(--t) var(--ease);
}
.drawer__list a:hover { padding-left: .6rem; color: var(--nav-accent, var(--brand-lift)); }
.drawer__list a:hover::before { transform: scale(1); opacity: 1; }

.drawer__foot { margin-top: auto; padding-top: 1.5rem; }

/* -------------------------------------------------- Lớp phủ tìm kiếm - */
.search-overlay {
  position: fixed;
  inset: 0;
  z-index: 130;
  display: grid;
  /* minmax(0,...) là bắt buộc: để cột tự co, nó lấy theo max-content của
     placeholder trong ô nhập và tràn khỏi màn hình hẹp. */
  grid-template-columns: minmax(0, 1fr);
  align-content: start;
  justify-items: center;
  padding: clamp(3rem, 12vh, 8rem) var(--pad-x) 2rem;
  background: var(--backdrop);
  backdrop-filter: blur(22px) saturate(150%);
  -webkit-backdrop-filter: blur(22px) saturate(150%);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--t) var(--ease), visibility var(--t);
}
.search-overlay.is-open { opacity: 1; visibility: visible; }

.search-overlay__inner {
  width: 100%;
  max-width: 700px;
  transform: translateY(-14px) scale(.98);
  transition: transform var(--t-slow) var(--ease-out);
}
.search-overlay.is-open .search-overlay__inner { transform: none; }

.search-form {
  display: flex;
  align-items: center;
  gap: .75rem;
  padding: .5rem .5rem .5rem 1.15rem;
  background: var(--bg-elev);
  border: 1px solid var(--line-strong);
  border-radius: var(--r-pill);
  box-shadow: var(--sh-lg);
}
.search-form input {
  flex: 1;
  min-width: 0;
  padding-block: .75rem;
  border: 0;
  background: transparent;
  font-size: var(--fs-md);
  outline: 0;
}
.search-form input::placeholder { color: var(--ink-4); }

.search-hints { display: flex; flex-wrap: wrap; gap: .5rem; margin-top: 1.1rem; }

/* ---------------------------------------------------------------- Lưới - */
.grid { display: grid; gap: var(--gap); }

.grid--2 { grid-template-columns: minmax(0, 1fr); }
@media (min-width: 700px) { .grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); } }

.grid--3 { grid-template-columns: repeat(auto-fill, minmax(min(100%, 270px), 1fr)); }
.grid--4 { grid-template-columns: repeat(auto-fill, minmax(min(100%, 220px), 1fr)); }

/* Nội dung + cột phụ */
.with-aside { display: grid; gap: clamp(1.5rem, 3vw, 2.5rem); align-items: start; }
@media (min-width: 1040px) {
  .with-aside { grid-template-columns: minmax(0, 1fr) 300px; }
  .with-aside--wide { grid-template-columns: minmax(0, 1fr) 340px; }
}

.aside-sticky { position: sticky; top: calc(var(--header-h) + 1.25rem); }

/* Hộp nền nổi dùng cho cột phụ và các panel phụ trợ */
.panel {
  padding: 1.15rem 1.25rem;
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  background: var(--bg-elev);
}

/* ---------------------------------------------------------------- Footer - */
.site-footer {
  margin-top: var(--section-y);
  padding-top: clamp(2.5rem, 5vw, 4rem);
  border-top: 1px solid var(--line);
  background: var(--bg-soft);
  color: var(--ink-2);
}

.footer-top {
  display: grid;
  gap: clamp(2rem, 4vw, 3rem);
  padding-bottom: clamp(2rem, 4vw, 3rem);
}
@media (min-width: 700px) { .footer-top { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
@media (min-width: 1040px) {
  .footer-top { grid-template-columns: 1.5fr 1.2fr .9fr 1.4fr; }
}

.footer-col h4 {
  margin-bottom: 1.1rem;
  font-size: var(--fs-base);
  font-weight: 700;
  color: var(--ink);
}
.footer-col p { font-size: var(--fs-sm); line-height: 1.7; max-width: 40ch; }

/* Cột "Danh mục" chia đôi như trong thiết kế */
.footer-links {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: .55rem 1rem;
}
.footer-links--single { grid-template-columns: minmax(0, 1fr); }
.footer-links a {
  font-size: var(--fs-sm);
  color: var(--ink-2);
  transition: color var(--t-fast) var(--ease);
}
.footer-links a:hover { color: var(--brand-lift); }

.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding-block: 1.35rem 1.75rem;
  border-top: 1px solid var(--line);
  font-size: var(--fs-xs);
  color: var(--ink-3);
}
.footer-bottom nav { display: flex; flex-wrap: wrap; gap: 1.25rem; }
.footer-bottom a:hover { color: var(--brand-lift); }

.social-row { display: flex; gap: .5rem; margin-top: 1.35rem; }
.social-row a {
  display: grid;
  place-items: center;
  width: 38px; height: 38px;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--bg-elev);
  color: var(--ink-2);
  transition: background var(--t-fast) var(--ease), color var(--t-fast) var(--ease),
              border-color var(--t-fast) var(--ease), transform var(--t-fast) var(--ease);
}
.social-row a:hover {
  background: var(--brand);
  border-color: var(--brand);
  color: var(--brand-fg);
  transform: translateY(-2px);
}

/* ------------------------------------------------------ Breakpoint lớn - */
@media (min-width: 1120px) {
  .nav { display: block; }
  .menu-btn { display: none; }
  .icon-btn__kbd { display: inline-block; }
}

/* Icon phản ánh chế độ đang bật: mặt trăng = đang nền tối, mặt trời = nền sáng */
.icon--sun { display: none; }
.icon--moon { display: block; }
:root[data-theme="light"] .icon--sun { display: block; }
:root[data-theme="light"] .icon--moon { display: none; }

/* Máy rất hẹp (<=380px): header không đủ chỗ cho cả nút chuyển ngôn ngữ,
   nên đưa xuống ngăn kéo menu. */
@media (max-width: 380px) {
  .header-actions .lang-switch { display: none; }
}
.drawer__foot .lang-switch { margin-top: .75rem; justify-content: center; }
@media (min-width: 381px) { .drawer__foot .lang-switch { display: none; } }