/* ============================================================================
   NHỊP — Reset, kiểu chữ nền và các lớp tiện ích dùng chung
   ============================================================================ */

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

* { margin: 0; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-h) + 1.5rem);
}

body {
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: var(--fs-base);
  line-height: var(--lh-body);
  font-synthesis-weight: none;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

body.is-locked { overflow: hidden; }

img, picture, video, canvas, svg { display: block; max-width: 100%; }
img { height: auto; background: var(--bg-sunken); }

input, button, textarea, select { font: inherit; color: inherit; }

p, h1, h2, h3, h4, h5, h6 { overflow-wrap: break-word; }

a { color: inherit; text-decoration: none; }

ul, ol { padding: 0; list-style: none; }

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: var(--r-xs);
}

::selection { background: var(--accent); color: var(--brand-fg); }

/* --- Tiêu đề ------------------------------------------------------------ */
h1, h2, h3, .display {
  font-family: var(--font-display);
  font-weight: 700;
  line-height: var(--lh-tight);
  letter-spacing: var(--tracking-tight);
}

h4, h5, h6 {
  font-family: var(--font-sans);
  font-weight: 700;
  line-height: var(--lh-snug);
  letter-spacing: var(--tracking-tight);
}

h1 { font-size: var(--fs-3xl); }
h2 { font-size: var(--fs-2xl); }
h3 { font-size: var(--fs-xl); }
h4 { font-size: var(--fs-lg); }

/* --- Thanh cuộn --------------------------------------------------------- */
@supports selector(::-webkit-scrollbar) {
  ::-webkit-scrollbar { width: 11px; height: 11px; }
  ::-webkit-scrollbar-track { background: var(--bg-soft); }
  ::-webkit-scrollbar-thumb {
    background: var(--line-strong);
    border: 3px solid var(--bg-soft);
    border-radius: var(--r-pill);
  }
  ::-webkit-scrollbar-thumb:hover { background: var(--ink-4); }
}

/* ============================================================================
   Tiện ích
   ============================================================================ */

.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--pad-x);
}

.container--narrow { max-width: var(--container-narrow); }

.section { padding-block: var(--section-y); }
.section--tight { padding-block: clamp(1.35rem, 2.4vw, 2.1rem); }
.section--soft { background: var(--bg-soft); }

.stack > * + * { margin-top: var(--flow, 1rem); }

.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

.skip-link {
  position: fixed;
  top: 0; left: 50%;
  transform: translate(-50%, -120%);
  z-index: 200;
  padding: .7rem 1.4rem;
  background: var(--accent);
  color: #fff;
  font-weight: 600;
  border-radius: 0 0 var(--r-md) var(--r-md);
  transition: transform var(--t) var(--ease-out);
}
.skip-link:focus { transform: translate(-50%, 0); }

/* Cắt chữ sau n dòng */
.clamp-1, .clamp-2, .clamp-3, .clamp-4 {
  display: -webkit-box;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.clamp-1 { -webkit-line-clamp: 1; }
.clamp-2 { -webkit-line-clamp: 2; }
.clamp-3 { -webkit-line-clamp: 3; }
.clamp-4 { -webkit-line-clamp: 4; }

.lede {
  font-size: var(--fs-md);
  line-height: 1.62;
  color: var(--ink-2);
}

.muted { color: var(--ink-3); }

.rule {
  height: 1px;
  border: 0;
  background: var(--line);
}

/* Ảnh giữ tỉ lệ, có hiệu ứng phóng nhẹ khi hover thẻ cha */
.ratio {
  position: relative;
  overflow: hidden;
  background: var(--bg-sunken);
  border-radius: var(--r-md);
}
.ratio > img,
.ratio > iframe {
  position: absolute;
  inset: 0;
  width: 100%; height: 100%;
  object-fit: cover;
  border: 0;
}
.ratio--16x9 { aspect-ratio: 16 / 9; }
.ratio--4x3  { aspect-ratio: 4 / 3; }
.ratio--3x2  { aspect-ratio: 3 / 2; }
.ratio--1x1  { aspect-ratio: 1 / 1; }
.ratio--3x4  { aspect-ratio: 3 / 4; }
.ratio--21x9 { aspect-ratio: 21 / 9; }

.icon {
  width: 1.25em; height: 1.25em;
  flex: none;
  fill: none;
  stroke: currentColor;
  stroke-width: 1.7;
  stroke-linecap: round;
  stroke-linejoin: round;
}

/* --- Hiệu ứng hiện dần khi cuộn tới -------------------------------------
   Chỉ ẩn khi trang thực sự có JS (lớp .has-js do script nhỏ trong <head> gắn).
   Nếu JS hỏng hoặc bị chặn, mọi nội dung vẫn hiển thị bình thường. */
.has-js .reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity .7s var(--ease-out), transform .7s var(--ease-out);
  transition-delay: var(--reveal-delay, 0ms);
}
.has-js .reveal.is-in { opacity: 1; transform: none; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .01ms !important;
  }
  .has-js .reveal { opacity: 1; transform: none; }
}