/* TIGP Modern Experimental Techniques — course website styles v2
   Look: lab-notebook-meets-instrument. Navy header with oscilloscope grid,
   serif display headings (Source Serif 4), Inter for UI/body, teal accent. */

:root {
  --bg: #f3f5f9;
  --card: #ffffff;
  --ink: #1b2536;
  --muted: #5a6b84;
  --line: #dde4ef;
  --brand-1: #0e2a52;
  --brand-2: #17518f;
  --accent: #0e8fa3;
  --accent-ink: #0b7080;
  --amber: #b45309;
  --serif: "Source Serif 4", Georgia, "Times New Roman", serif;
  --sans: "Inter", -apple-system, "Segoe UI", Arial, sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: var(--sans);
  font-size: 16px;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.6;
}
::selection { background: #bfe3ea; }

/* ---------- header ---------- */
header {
  padding: 34px 16px 26px;
  color: #fff;
  background:
    linear-gradient(rgba(255,255,255,0.045) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.045) 1px, transparent 1px),
    linear-gradient(135deg, var(--brand-1) 0%, var(--brand-2) 100%);
  background-size: 26px 26px, 26px 26px, 100% 100%;
  border-bottom: 3px solid var(--accent);
}
.brand-wrap {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 18px;
  flex-wrap: wrap;
}
.brand-title {
  margin: 0;
  font-family: var(--serif);
  font-size: 2.3rem;
  font-weight: 700;
  letter-spacing: 0.01em;
  line-height: 1.15;
  text-wrap: balance;
}
.brand-title a { color: inherit; text-decoration: none; }
.brand-title a:hover { color: #cfe6f3; }
.brand-subtitle {
  margin: 8px 0 0;
  color: #c9d9ef;
  font-size: 1.02rem;
  line-height: 1.5;
  max-width: 62em;
}
.brand-zh { color: #8fa9cc; font-size: 0.95rem; }

/* ---------- nav ---------- */
nav {
  background: #0b1f3d;
  padding: 8px 12px;
  position: sticky;
  top: 0;
  z-index: 10;
  box-shadow: 0 2px 10px rgba(10, 25, 50, 0.25);
}
.menu {
  margin: 0 auto; padding: 0; list-style: none; max-width: 1100px;
  display: flex; gap: 4px; justify-content: center; flex-wrap: wrap;
}
.menu a {
  text-decoration: none; color: #dbe6f5; font-weight: 600;
  font-size: 0.95rem; letter-spacing: 0.01em;
  display: block; padding: 7px 14px; border-radius: 999px;
  transition: background 0.15s, color 0.15s;
}
.menu a:hover { background: rgba(255,255,255,0.10); color: #fff; }
.menu a.active { background: var(--accent); color: #fff; }


/* language switch pill */
.menu a.lang {
  border: 1px solid rgba(255,255,255,0.35);
  margin-left: 10px;
}

/* ---------- layout ---------- */
main { max-width: 1100px; margin: 0 auto; padding: 30px 16px 48px; }

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 24px 28px;
  margin-bottom: 20px;
  box-shadow: 0 1px 3px rgba(20, 35, 60, 0.05), 0 6px 24px -18px rgba(20, 35, 60, 0.25);
}
.card h1 {
  margin: 0 0 14px;
  font-family: var(--serif);
  font-size: 1.95rem;
  font-weight: 700;
  line-height: 1.2;
  text-wrap: balance;
}
.card h2 {
  margin: 28px 0 12px;
  font-family: var(--serif);
  font-size: 1.45rem;
  font-weight: 600;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--line);
}
.card h2::before {
  content: "";
  display: inline-block;
  width: 26px; height: 4px;
  border-radius: 2px;
  background: var(--accent);
  margin-right: 10px;
  vertical-align: 0.28em;
}
.card h2:first-child { margin-top: 0; }
.card h3 { margin: 18px 0 6px; font-size: 1.12rem; font-weight: 700; }
.card p, .card li { margin: 7px 0; }
.card ul, .card ol { padding-left: 1.4em; }

a { color: var(--accent-ink); text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { color: var(--brand-2); }

strong { color: #101a2b; }

/* ---------- code ---------- */
code, pre {
  font-family: Consolas, "Cascadia Code", "Courier New", monospace;
  font-size: 0.92em;
  background: #eef2f8;
  border-radius: 6px;
}
code { padding: 1px 6px; }
pre {
  padding: 14px 16px;
  overflow-x: auto;
  border: 1px solid var(--line);
  border-left: 4px solid var(--accent);
  line-height: 1.5;
}
pre code { background: none; padding: 0; }

/* ---------- tables ---------- */
table { border-collapse: collapse; width: 100%; margin: 12px 0; font-size: 0.95em; }
th, td { border: 1px solid var(--line); padding: 8px 12px; text-align: left; vertical-align: top; }
th {
  background: #eaf0f8;
  color: #24344f;
  font-size: 0.85em;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
tr:nth-child(even) td { background: #f7f9fc; }
.table-wrap { overflow-x: auto; }

/* ---------- hero / facts ---------- */
.hero { display: flex; gap: 28px; align-items: flex-start; flex-wrap: wrap; }
.hero .facts { flex: 1 1 280px; }
.facts dl {
  display: grid; grid-template-columns: max-content 1fr; gap: 8px 14px; margin: 0;
  background: #f2f7fa;
  border: 1px solid #d8e6ec;
  border-radius: 12px;
  padding: 16px 18px;
}
.facts dt {
  font-size: 0.74em; font-weight: 700; color: var(--accent-ink);
  text-transform: uppercase; letter-spacing: 0.07em; padding-top: 0.35em;
}
.facts dd { margin: 0; font-size: 0.97em; }

/* ---------- tiles ---------- */
.grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); gap: 16px; margin: 12px 0; }
.tile {
  background: var(--card);
  border: 1px solid var(--line);
  border-top: 3px solid var(--accent);
  border-radius: 12px;
  padding: 16px 18px;
  box-shadow: 0 1px 3px rgba(20, 35, 60, 0.05);
  transition: transform 0.15s, box-shadow 0.15s;
}
.tile:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px -12px rgba(20, 35, 60, 0.35);
}
.tile h3 { margin: 0 0 6px; font-size: 1.08rem; font-weight: 700; }
.tile p { margin: 4px 0; font-size: 0.94em; color: #33415a; }
.tile .tag {
  display: inline-block; font-size: 0.72em; font-weight: 700;
  padding: 2px 9px; border-radius: 999px; margin-bottom: 8px;
  letter-spacing: 0.04em; text-transform: uppercase;
  background: #e0e7ff; color: #1e3a8a;
}
.tile .tag.a { background: #d5f0dd; color: #14532d; }
.tile .tag.b { background: #fdeec9; color: #7c4a03; }
.tile .tag.c { background: #fbdcdc; color: #7f1d1d; }
.tile:has(.tag.a) { border-top-color: #34a862; }
.tile:has(.tag.b) { border-top-color: #dfa018; }
.tile:has(.tag.c) { border-top-color: #d05252; }

/* ---------- callouts ---------- */
.callout {
  border-left: 4px solid var(--accent);
  background: #eaf6f8;
  padding: 12px 16px;
  border-radius: 0 12px 12px 0;
  margin: 14px 0;
}
.callout.warn { border-color: var(--amber); background: #fff8e9; }
.callout.todo { border-color: #9ca3af; background: #f3f4f6; color: #4b5563; }
.callout.todo::before { content: "TO COME · "; font-size: 0.75em; font-weight: 700; letter-spacing: 0.06em; color: #6b7280; }

/* ---------- steps ---------- */
.steps { counter-reset: step; list-style: none; padding-left: 0; }
.steps > li {
  position: relative;
  padding: 2px 0 14px 3.0em;
  margin: 0;
  border-left: 2px solid var(--line);
  margin-left: 1.05em;
}
.steps > li:last-child { border-left-color: transparent; }
.steps > li::before {
  counter-increment: step; content: counter(step);
  position: absolute; left: -1.15em; top: 0;
  width: 2.1em; height: 2.1em; border-radius: 50%;
  background: linear-gradient(135deg, var(--brand-2), var(--accent));
  color: #fff; font-weight: 700; font-size: 0.95em;
  display: flex; align-items: center; justify-content: center;
  box-shadow: 0 2px 6px rgba(14, 42, 82, 0.3);
}
.steps h3 { margin: 0 0 4px; }
.check { color: #15803d; font-weight: 700; }

/* ---------- footer ---------- */
footer {
  background: var(--brand-1);
  color: #b9c9e2;
  padding: 26px 16px;
  font-size: 0.92em;
  border-top: 3px solid var(--accent);
}
footer a { color: #9fd4de; }
footer a:hover { color: #fff; }
.footer-stack {
  max-width: 1100px; margin: 0 auto;
  display: flex; gap: 20px; align-items: center; flex-wrap: wrap; justify-content: space-between;
}
.footer-stack p { margin: 2px 0; }

/* ---------- responsive ---------- */
@media (max-width: 640px) {
  .brand-title { font-size: 1.55rem; }
  .card { padding: 16px 18px; }
  body { font-size: 15px; }
}

@media print {
  nav { position: static; }
  .tile, .card { box-shadow: none; }
}