/* ============================================================
   THE NEURO RESET — hệ thống thiết kế dùng chung cho mọi trang
   Thiết kế cho độc giả 50–75 tuổi: chữ to, tương phản đạt WCAG AA,
   vùng chạm tối thiểu 48px, không hiệu ứng gây chóng mặt.
   ============================================================ */

:root {
  --ink: #0d1a24;
  --ink-soft: #24333e;
  --paper: #f4f6f3;
  --paper-2: #ffffff;
  --line: #d7ddd6;
  /* Viền cho phần tử tương tác. #6b7a72 trên --paper = 4.0:1 (WCAG 1.4.11 cần 3:1) */
  --line-strong: #6b7a72;
  --muted: #5c6b66;
  --jade: #17998a;
  --jade-deep: #0f6f65;
  --amber: #d98a2b;
  --amber-deep: #b9711b;
  --alert: #8a3b12;
  --shadow: 0 1px 2px rgba(13,26,36,.06), 0 12px 32px -12px rgba(13,26,36,.18);
  --radius: 14px;
  --maxw: 1120px;
  --readw: 760px;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Times New Roman", serif;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", "Cascadia Code", "Roboto Mono", Menlo, Consolas, monospace;
}
@media (prefers-color-scheme: dark) {
  :root {
    --ink: #eaf1ec; --ink-soft: #c3d0c9; --paper: #0b1418; --paper-2: #101c22;
    --line: #22333a; --line-strong: #5a6d75; --muted: #8fa39b;
    --jade: #35c3b0; --jade-deep: #35c3b0; --amber: #e8a44a; --amber-deep: #e8a44a; --alert: #ffb37a;
    --shadow: 0 1px 2px rgba(0,0,0,.4), 0 18px 40px -18px rgba(0,0,0,.6);
  }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce){ html { scroll-behavior: auto; } }

body {
  margin: 0; background: var(--paper); color: var(--ink);
  font-family: var(--sans);
  /* 18px cơ sở — không hạ xuống. Độc giả phần lớn trên 55 tuổi. */
  font-size: 18px; line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}
h1, h2, h3, h4 { font-family: var(--serif); font-weight: 600; line-height: 1.15;
  text-wrap: balance; letter-spacing: -.01em; margin: 0; }
p { margin: 0 0 16px; }
a { color: var(--jade-deep); text-decoration: underline; text-underline-offset: 3px; }

/* FOCUS — mọi phần tử tương tác phải thấy rõ khi đi bằng bàn phím */
a:focus-visible, button:focus-visible, input:focus-visible,
summary:focus-visible, [tabindex]:focus-visible {
  outline: 3px solid var(--jade-deep); outline-offset: 3px; border-radius: 6px;
}

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }
.read { max-width: var(--readw); margin: 0 auto; padding: 0 24px; }
.eyebrow { font-family: var(--mono); font-size: 13px; letter-spacing: .16em;
  text-transform: uppercase; color: var(--jade-deep); font-weight: 600; }

/* Bỏ qua điều hướng — cho người dùng bàn phím và trình đọc màn hình */
.skip { position: absolute; left: -9999px; top: 0; background: var(--jade-deep);
  color: #fff; padding: 14px 20px; z-index: 200; border-radius: 0 0 10px 0; }
.skip:focus { left: 0; }

/* ---------- NÚT ---------- */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: .5em;
  font-family: var(--sans); font-weight: 600; font-size: 17px; padding: 15px 26px;
  border-radius: 999px; border: 1.5px solid transparent; cursor: pointer;
  text-decoration: none; min-height: 52px; transition: background .2s ease, transform .15s ease; }
.btn-primary { background: var(--amber); color: #1c1206; box-shadow: var(--shadow); }
.btn-primary:hover { background: var(--amber-deep); transform: translateY(-1px); }
.btn-ghost { background: transparent; color: var(--ink); border-color: var(--line-strong); }
.btn-ghost:hover { border-color: var(--jade); color: var(--jade-deep); }
@media (prefers-reduced-motion: reduce){ .btn:hover { transform: none; } }

/* ---------- ĐIỀU HƯỚNG ---------- */
.nav { position: sticky; top: 0; z-index: 50; background: var(--paper-2);
  border-bottom: 1px solid var(--line); }
.nav-in { display: flex; align-items: center; justify-content: space-between;
  gap: 16px; height: 70px; }
.brand { display: inline-flex; align-items: center; gap: 11px; font-family: var(--serif);
  font-weight: 600; font-size: 20px; color: var(--ink); text-decoration: none; flex: none; }
.brand img.mark { width: 34px; height: 34px; flex: none; border-radius: 50%; display: block; }
.nav-links { display: flex; align-items: center; gap: 26px; }
.nav-links a { font-size: 16px; color: var(--ink-soft); font-weight: 500; text-decoration: none; }
.nav-links a:hover { color: var(--jade-deep); text-decoration: underline; }
.nav-links a[aria-current="page"] { color: var(--jade-deep); font-weight: 700; }
.nav-cta { display: flex; align-items: center; gap: 12px; flex: none; }
.nav-cta .btn { font-size: 15px; padding: 11px 18px; min-height: 44px; }

/* Hamburger — 48x48 để ngón tay viêm khớp bấm trúng */
.nav-burger { display: none; width: 48px; height: 48px; flex: none;
  align-items: center; justify-content: center; background: transparent;
  border: 1.5px solid var(--line-strong); border-radius: 12px; cursor: pointer; color: var(--ink); }
.nav-burger svg { width: 24px; height: 24px; }
.nav-burger .ic-close { display: none; }
.nav[data-open="true"] .nav-burger .ic-close { display: block; }
.nav[data-open="true"] .nav-burger .ic-open { display: none; }

@media (max-width: 980px){
  .nav-burger { display: inline-flex; }
  .nav-links { position: absolute; left: 0; right: 0; top: 70px; display: none;
    flex-direction: column; align-items: stretch; gap: 0; padding: 8px 24px 18px;
    background: var(--paper-2); border-bottom: 1px solid var(--line-strong); box-shadow: var(--shadow); }
  .nav[data-open="true"] .nav-links { display: flex; }
  /* Mỗi mục cao 56px — bấm bằng ngón cái được */
  .nav-links a { font-size: 18px; padding: 16px 4px; min-height: 56px; display: flex;
    align-items: center; border-bottom: 1px solid var(--line); }
  .nav-links a:last-child { border-bottom: none; }
}
@media (max-width: 520px){ .nav-cta .btn { font-size: 14px; padding: 10px 12px; } }

/* ---------- BREADCRUMB — người lớn tuổi cần biết mình đang ở đâu ---------- */
.crumb { font-size: 16px; color: var(--muted); padding: 20px 0 0; }
.crumb a { color: var(--muted); }
.crumb span { padding: 0 6px; }

/* ---------- BỐ CỤC TRANG ---------- */
.page-head { padding: 20px 0 8px; }
.page-head h1 { font-size: clamp(32px, 5.2vw, 48px); margin-bottom: 14px; }
.page-head .lead { font-size: 20px; color: var(--ink-soft); max-width: 60ch; }
main { padding-bottom: 20px; }
section { padding: 34px 0; }
h2 { font-size: clamp(24px, 3.4vw, 32px); margin: 0 0 14px; }
h3 { font-size: clamp(19px, 2.4vw, 22px); margin: 26px 0 8px; }
ul, ol { padding-left: 24px; margin: 0 0 16px; }
li { margin-bottom: 8px; color: var(--ink-soft); }

/* ---------- THẺ ---------- */
.grid { display: grid; gap: 18px; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
@media (max-width: 860px){ .grid-2, .grid-3 { grid-template-columns: 1fr; } }

.card { background: var(--paper-2); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 26px; display: block; text-decoration: none; color: inherit; }
a.card:hover { border-color: var(--jade); box-shadow: var(--shadow); }
.card h3 { font-size: 21px; margin: 0 0 8px; }
.card p { color: var(--ink-soft); font-size: 17px; margin: 0; }
.card .more { display: inline-block; margin-top: 12px; color: var(--jade-deep);
  font-weight: 600; font-size: 16px; }

/* ---------- KHỐI CHÚ Ý ---------- */
.note { background: var(--paper-2); border: 1px solid var(--line-strong);
  border-radius: var(--radius); padding: 22px 24px; margin: 26px 0; }
.note p:last-child { margin-bottom: 0; }
.note-safety { border-color: var(--amber-deep);
  background: color-mix(in srgb, var(--amber) 8%, var(--paper-2)); }

/* Khối ghi chú nội bộ — PHẢI XOÁ trước khi đẩy lên hosting */
.todo { border: 2px dashed var(--amber-deep);
  background: color-mix(in srgb, var(--amber) 10%, var(--paper-2));
  border-radius: var(--radius); padding: 20px 22px; margin: 26px 0; font-size: 16px; }
.todo strong { color: var(--amber-deep); }
.todo p:last-child { margin-bottom: 0; }

/* ---------- GIÁ ---------- */
.price { font-family: var(--serif); font-size: 40px; font-weight: 600; color: var(--ink); }
.price small { font-size: 17px; color: var(--muted); font-family: var(--sans); font-weight: 400; }

/* ---------- CTA CUỐI TRANG ---------- */
.endcta { background: var(--paper-2); border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line); padding: 44px 0; margin-top: 40px; text-align: center; }
.endcta h2 { margin-bottom: 10px; }
.endcta p { color: var(--ink-soft); max-width: 52ch; margin: 0 auto 22px; }

/* Đọc tiếp — không trang nào được là ngõ cụt */
.next { border-top: 1px solid var(--line); margin-top: 34px; padding-top: 24px; }
.next h4 { font-size: 17px; color: var(--muted); font-weight: 600; margin-bottom: 12px;
  font-family: var(--sans); letter-spacing: .04em; text-transform: uppercase; }

/* ---------- CHÂN TRANG ---------- */
footer.site { border-top: 1px solid var(--line); background: var(--paper-2);
  margin-top: 0; padding: 44px 0 40px; }
.ft-in { display: grid; grid-template-columns: 1.4fr repeat(3, 1fr); gap: 30px; }
@media (max-width: 860px){ .ft-in { grid-template-columns: 1fr 1fr; } }
@media (max-width: 520px){ .ft-in { grid-template-columns: 1fr; } }
.ft-in h4 { font-family: var(--sans); font-size: 15px; letter-spacing: .06em;
  text-transform: uppercase; color: var(--muted); margin: 0 0 12px; }
.ft-in a { display: block; color: var(--ink-soft); text-decoration: none;
  font-size: 17px; padding: 7px 0; min-height: 40px; }
.ft-in a:hover { color: var(--jade-deep); text-decoration: underline; }
.ft-about { color: var(--ink-soft); font-size: 17px; margin-top: 14px; max-width: 34ch; }
.disclaimer { border-top: 1px solid var(--line); margin-top: 30px; padding-top: 22px;
  font-size: 15.5px; color: var(--ink-soft); line-height: 1.65; }
.disclaimer p { margin: 0 0 10px; }
.ft-bottom { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 12px;
  margin-top: 22px; font-size: 16px; color: var(--muted); }
.ft-bottom a { color: var(--muted); }

/* --- Bai viet trong /learn/ (them 13/09/2026) --- */
.article{max-width:720px}
.article h2{margin:34px 0 12px;font-size:1.45rem;line-height:1.3}
.article p{margin:0 0 18px}
.article ul{margin:0 0 18px 22px}
.article li{margin-bottom:8px}
.fig{margin:26px 0 30px}
.fig img{width:100%;height:auto;border-radius:14px;display:block;
  border:1px solid var(--line,#dcdcd6)}
.fig figcaption{margin-top:10px;font-size:.95rem;line-height:1.5;
  color:var(--muted,#5b6560)}
.byline{margin-top:14px;font-size:.98rem;color:var(--muted,#5b6560)}
.byline a{color:inherit}
@media (max-width:640px){.article h2{font-size:1.3rem}}