/* ==========================================================================
   Style chung cho toàn bộ website
   Sửa màu sắc / font ở phần :root bên dưới là đổi được cả site.
   ========================================================================== */

:root {
  --brand: #12518a;
  --brand-dark: #0d3c68;
  --brand-light: #e8f1fa;
  --accent: #e8912a;
  --accent-dark: #c9761a;

  --bg: #ffffff;
  --bg-alt: #f5f7fa;
  --surface: #ffffff;
  --text: #16212e;
  --muted: #5b6b7c;
  --border: #dde4ec;

  --ok: #1a7f4b;
  --warn: #b4520c;
  --err: #c02626;

  --radius: 10px;
  --radius-sm: 6px;
  --shadow: 0 1px 2px rgba(16, 33, 46, .06), 0 8px 24px rgba(16, 33, 46, .07);
  --shadow-sm: 0 1px 2px rgba(16, 33, 46, .08);
  --wrap: 1160px;

  --font: "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: "Cascadia Mono", Consolas, "SF Mono", Menlo, monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --brand: #4a9be0;
    --brand-dark: #2f7cbd;
    --brand-light: #16283a;
    --accent: #f0a441;
    --accent-dark: #d5872a;

    --bg: #0f151c;
    --bg-alt: #151d26;
    --surface: #18212b;
    --text: #e6edf5;
    --muted: #93a3b5;
    --border: #2a3644;

    --ok: #48c98a;
    --warn: #e8a054;
    --err: #f0736a;

    --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 8px 24px rgba(0, 0, 0, .35);
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, .4);
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.65;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 { line-height: 1.25; margin: 0 0 .6em; font-weight: 700; }
h1 { font-size: clamp(1.9rem, 1.2rem + 2.6vw, 3rem); letter-spacing: -.02em; }
h2 { font-size: clamp(1.5rem, 1.1rem + 1.4vw, 2.1rem); letter-spacing: -.01em; }
h3 { font-size: 1.18rem; }
p { margin: 0 0 1em; }

a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }

img { max-width: 100%; height: auto; display: block; }

code, kbd { font-family: var(--mono); font-size: .92em; }

.wrap { max-width: var(--wrap); margin: 0 auto; padding: 0 20px; }
.narrow { max-width: 820px; }

/* ---------- Header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: saturate(150%) blur(10px);
  border-bottom: 1px solid var(--border);
}

.site-header .wrap {
  display: flex;
  align-items: center;
  gap: 24px;
  min-height: 64px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  font-size: 1.12rem;
  color: var(--text);
  letter-spacing: -.02em;
  white-space: nowrap;
}
.logo:hover { text-decoration: none; }
/* Logo của app GnadStructure — file assets/img/logo.png, nền trong suốt */
.logo .mark {
  width: 38px;
  height: 38px;
  flex: none;
  object-fit: contain;
}
.logo small { display: block; font-size: .68rem; font-weight: 500; color: var(--muted); letter-spacing: .04em; text-transform: uppercase; }

.nav { margin-left: auto; display: flex; align-items: center; gap: 4px; }
.nav a {
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  color: var(--muted);
  font-weight: 600;
  font-size: .95rem;
}
.nav a:hover { background: var(--bg-alt); color: var(--text); text-decoration: none; }
.nav a.active { color: var(--brand); background: var(--brand-light); }

.nav-toggle {
  display: none;
  margin-left: auto;
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text);
  font-size: 1.3rem;
  line-height: 1;
  padding: 6px 11px;
  cursor: pointer;
}

@media (max-width: 860px) {
  .nav-toggle { display: block; }
  .nav {
    display: none;
    position: absolute;
    top: 100%; left: 0; right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 8px;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow);
  }
  .nav.open { display: flex; }
  .nav a { padding: 12px; }
}

/* ---------- Nút ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 11px 20px;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: .96rem;
  font-family: inherit;
  cursor: pointer;
  transition: background .15s, border-color .15s, transform .1s;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn:active { transform: none; }

.btn-primary { background: var(--brand); color: #fff; }
.btn-primary:hover { background: var(--brand-dark); }

.btn-accent { background: var(--accent); color: #201401; }
.btn-accent:hover { background: var(--accent-dark); }

.btn-ghost { background: transparent; color: var(--text); border-color: var(--border); }
.btn-ghost:hover { background: var(--bg-alt); }

.btn-sm { padding: 7px 14px; font-size: .88rem; }

/* ---------- Hero ---------- */
.hero {
  position: relative;
  overflow: hidden;
  background:
    radial-gradient(900px 420px at 12% -10%, color-mix(in srgb, var(--brand) 22%, transparent), transparent 65%),
    radial-gradient(700px 400px at 92% 8%, color-mix(in srgb, var(--accent) 16%, transparent), transparent 60%),
    var(--bg-alt);
  border-bottom: 1px solid var(--border);
  padding: 72px 0 64px;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.15fr .85fr;
  gap: 48px;
  align-items: center;
}
@media (max-width: 900px) {
  .hero { padding: 48px 0 44px; }
  .hero-grid { grid-template-columns: 1fr; gap: 32px; }
}

.eyebrow {
  display: inline-block;
  padding: 5px 12px;
  margin-bottom: 18px;
  border-radius: 999px;
  background: var(--brand-light);
  color: var(--brand);
  font-size: .78rem;
  font-weight: 700;
  letter-spacing: .06em;
  text-transform: uppercase;
}

.hero .lead { font-size: 1.1rem; color: var(--muted); max-width: 56ch; }

.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 26px; }

.check-list { list-style: none; margin: 26px 0 0; padding: 0; display: grid; gap: 10px; }
.check-list li { position: relative; padding-left: 30px; color: var(--muted); }
.check-list li::before {
  content: "✓";
  position: absolute; left: 0; top: -1px;
  width: 20px; height: 20px;
  display: grid; place-items: center;
  border-radius: 50%;
  background: color-mix(in srgb, var(--ok) 16%, transparent);
  color: var(--ok);
  font-size: .74rem;
  font-weight: 800;
}

/* Khối minh hoạ trong hero */
.hero-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
}
.hero-card header {
  padding: 12px 16px;
  background: var(--bg-alt);
  border-bottom: 1px solid var(--border);
  font-size: .82rem;
  font-weight: 700;
  color: var(--muted);
  letter-spacing: .03em;
  text-transform: uppercase;
}
.hero-card .body { padding: 16px; }
.kv { display: grid; grid-template-columns: 1fr auto; gap: 6px 16px; font-size: .94rem; }
.kv dt { color: var(--muted); }
.kv dd { margin: 0; font-family: var(--mono); font-weight: 600; }

/* ---------- Section ---------- */
.section { padding: 72px 0; }
.section.alt { background: var(--bg-alt); border-block: 1px solid var(--border); }
@media (max-width: 700px) { .section { padding: 48px 0; } }

.section-head { max-width: 720px; margin-bottom: 40px; }
.section-head.center { margin-inline: auto; text-align: center; }
.section-head p { color: var(--muted); font-size: 1.05rem; margin: 0; }

/* ---------- Lưới thẻ ---------- */
.grid { display: grid; gap: 20px; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }
@media (max-width: 980px) { .grid-3, .grid-4 { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 640px) { .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; } }

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px;
  box-shadow: var(--shadow-sm);
  transition: border-color .15s, box-shadow .15s, transform .15s;
}
.card:hover { border-color: color-mix(in srgb, var(--brand) 45%, var(--border)); box-shadow: var(--shadow); transform: translateY(-2px); }
.card h3 { margin-bottom: .4em; }
.card p { color: var(--muted); font-size: .95rem; margin-bottom: 0; }
.card .icon {
  width: 42px; height: 42px;
  display: grid; place-items: center;
  margin-bottom: 14px;
  border-radius: 9px;
  background: var(--brand-light);
  color: var(--brand);
  font-size: 1.25rem;
}

/* Thẻ phần mềm */
.soft-card { display: flex; flex-direction: column; }
.soft-card .code {
  font-family: var(--mono);
  font-size: .74rem;
  font-weight: 700;
  letter-spacing: .06em;
  color: var(--accent-dark);
  text-transform: uppercase;
}
@media (prefers-color-scheme: dark) { .soft-card .code { color: var(--accent); } }
.soft-card h3 { font-size: 1.05rem; margin: 4px 0 8px; }
.soft-card .std {
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px dashed var(--border);
  font-size: .82rem;
  color: var(--muted);
}
.soft-card .foot { margin-top: auto; padding-top: 14px; display: flex; gap: 8px; }

.tag {
  display: inline-block;
  padding: 2px 9px;
  border-radius: 999px;
  background: var(--bg-alt);
  border: 1px solid var(--border);
  font-size: .76rem;
  font-weight: 600;
  color: var(--muted);
}

/* Bộ lọc */
.filters { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 28px; }
.filter-btn {
  padding: 8px 16px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  color: var(--muted);
  font-family: inherit;
  font-size: .9rem;
  font-weight: 600;
  cursor: pointer;
}
.filter-btn:hover { border-color: var(--brand); color: var(--text); }
.filter-btn.active { background: var(--brand); border-color: var(--brand); color: #fff; }

/* ---------- Số liệu ---------- */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1px; background: var(--border); border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; }
@media (max-width: 700px) { .stats { grid-template-columns: repeat(2, 1fr); } }
.stat { background: var(--surface); padding: 24px 20px; text-align: center; }
.stat b { display: block; font-size: 1.9rem; line-height: 1.1; color: var(--brand); letter-spacing: -.02em; }
.stat span { font-size: .86rem; color: var(--muted); }

/* ---------- Form / công cụ tính ---------- */
.calc {
  display: grid;
  grid-template-columns: minmax(0, 420px) minmax(0, 1fr);
  gap: 24px;
  align-items: start;
}
@media (max-width: 900px) { .calc { grid-template-columns: 1fr; } }

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
}
.panel > header {
  padding: 14px 20px;
  background: var(--bg-alt);
  border-bottom: 1px solid var(--border);
  font-weight: 700;
  font-size: .95rem;
}
.panel > .body { padding: 20px; }

fieldset { border: none; margin: 0 0 18px; padding: 0; }
fieldset legend {
  padding: 0 0 10px;
  font-size: .78rem;
  font-weight: 700;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--muted);
}

.field { margin-bottom: 14px; }
.field label { display: block; margin-bottom: 5px; font-size: .88rem; font-weight: 600; }
.field .hint { display: block; margin-top: 4px; font-size: .78rem; color: var(--muted); font-weight: 400; }

.row { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }

input[type="number"], input[type="text"], input[type="email"], select, textarea {
  width: 100%;
  padding: 9px 11px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg);
  color: var(--text);
  font-family: var(--mono);
  font-size: .95rem;
}
select, textarea { font-family: var(--font); }
textarea { resize: vertical; min-height: 130px; }

input:focus, select:focus, textarea:focus {
  outline: 2px solid color-mix(in srgb, var(--brand) 55%, transparent);
  outline-offset: 1px;
  border-color: var(--brand);
}

/* Kết quả */
.result-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 1px; background: var(--border); border: 1px solid var(--border); border-radius: var(--radius-sm); overflow: hidden; margin-bottom: 18px; }
.result-item { background: var(--surface); padding: 14px 16px; }
.result-item span { display: block; font-size: .78rem; color: var(--muted); margin-bottom: 2px; }
.result-item b { font-family: var(--mono); font-size: 1.15rem; font-weight: 700; }

.verdict {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 14px 16px;
  border-radius: var(--radius-sm);
  border: 1px solid;
  margin-bottom: 14px;
  font-size: .94rem;
}
.verdict .sym { font-size: 1.15rem; line-height: 1.4; }
.verdict.pass { background: color-mix(in srgb, var(--ok) 10%, transparent); border-color: color-mix(in srgb, var(--ok) 40%, transparent); color: var(--ok); }
.verdict.fail { background: color-mix(in srgb, var(--err) 10%, transparent); border-color: color-mix(in srgb, var(--err) 40%, transparent); color: var(--err); }
.verdict.note { background: color-mix(in srgb, var(--warn) 10%, transparent); border-color: color-mix(in srgb, var(--warn) 40%, transparent); color: var(--warn); }
.verdict b { color: inherit; }

.formula {
  padding: 12px 14px;
  background: var(--bg-alt);
  border-left: 3px solid var(--brand);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  font-family: var(--mono);
  font-size: .88rem;
  color: var(--muted);
  overflow-x: auto;
  white-space: nowrap;
}

/* ---------- Bảng ---------- */
.table-scroll { overflow-x: auto; -webkit-overflow-scrolling: touch; }
table.data {
  width: 100%;
  min-width: 520px;
  border-collapse: collapse;
  font-size: .92rem;
}
table.data th, table.data td {
  padding: 9px 12px;
  border-bottom: 1px solid var(--border);
  text-align: left;
}
table.data th {
  background: var(--bg-alt);
  font-size: .8rem;
  letter-spacing: .04em;
  text-transform: uppercase;
  color: var(--muted);
  white-space: nowrap;
}
table.data td.num { font-family: var(--mono); text-align: right; }
table.data tbody tr:hover { background: var(--bg-alt); }

/* ---------- Bài viết ---------- */
.post-list { display: grid; gap: 1px; background: var(--border); border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; }
.post {
  display: grid;
  grid-template-columns: 108px 1fr;
  gap: 20px;
  padding: 20px 22px;
  background: var(--surface);
}
.post:hover { background: var(--bg-alt); }
.post time { font-size: .84rem; color: var(--muted); font-family: var(--mono); }
.post h3 { font-size: 1.05rem; margin-bottom: .3em; }
.post p { margin: 0; font-size: .93rem; color: var(--muted); }
@media (max-width: 640px) { .post { grid-template-columns: 1fr; gap: 6px; } }

/* ---------- CTA ---------- */
.cta {
  padding: 48px 40px;
  border-radius: var(--radius);
  background: linear-gradient(135deg, var(--brand), var(--brand-dark));
  color: #fff;
  text-align: center;
}
.cta h2 { color: #fff; }
.cta p { color: rgba(255, 255, 255, .85); max-width: 56ch; margin-inline: auto; }
.cta .hero-actions { justify-content: center; }
.cta .btn-ghost { color: #fff; border-color: rgba(255, 255, 255, .45); }
.cta .btn-ghost:hover { background: rgba(255, 255, 255, .12); }
@media (max-width: 640px) { .cta { padding: 36px 22px; } }

/* ---------- Footer ---------- */
.site-footer {
  background: var(--bg-alt);
  border-top: 1px solid var(--border);
  padding: 48px 0 28px;
  font-size: .93rem;
}
.footer-grid { display: grid; grid-template-columns: 1.6fr 1fr 1fr; gap: 36px; }
@media (max-width: 780px) { .footer-grid { grid-template-columns: 1fr; gap: 26px; } }
.site-footer h4 { font-size: .8rem; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); margin-bottom: 12px; }
.site-footer ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 7px; }
.site-footer a { color: var(--text); }
.site-footer p { color: var(--muted); }
.footer-bottom {
  margin-top: 32px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: .86rem;
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: space-between;
}

/* ---------- Tiện ích ---------- */
.disclaimer {
  padding: 14px 16px;
  border: 1px dashed var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-alt);
  color: var(--muted);
  font-size: .87rem;
}
.mt-0 { margin-top: 0; }
.mb-0 { margin-bottom: 0; }
.center { text-align: center; }
.hidden { display: none !important; }