:root {
  --bg: #f7f4ec;
  --panel: #ffffff;
  --ink: #1f2937;
  --ink-soft: #4b5563;
  --border: #d9d0bf;
  --accent: #0f766e;
  --accent-dark: #0b5b55;
  --note: #eef7ff;
  --warn: #fff7e8;
  --ok: #edf8f2;
  --code: #1e293b;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Segoe UI", "Inter", "Helvetica Neue", Arial, sans-serif;
  line-height: 1.6;
  color: var(--ink);
  background:
    radial-gradient(circle at 10% 10%, #eaf4f2 0, transparent 35%),
    radial-gradient(circle at 90% 0%, #f8ecd8 0, transparent 28%),
    linear-gradient(to right, rgba(28, 37, 51, 0.04) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(28, 37, 51, 0.04) 1px, transparent 1px),
    var(--bg);
  background-size: auto, auto, 28px 28px, 28px 28px, auto;
}

.page {
  width: min(1060px, 92vw);
  margin: 28px auto;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 14px;
}

.back-link {
  color: var(--accent);
  text-decoration: none;
  font-weight: 700;
}

.back-link:hover {
  text-decoration: underline;
}

.semester-badge {
  padding: 5px 10px;
  border-radius: 999px;
  border: 1px solid #8cc6c1;
  background: #e8f7f5;
  color: var(--accent-dark);
  font-size: 0.88rem;
  font-weight: 700;
}

article {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 28px;
  box-shadow: 0 18px 40px rgba(31, 41, 55, 0.08);
}

h1 {
  margin: 0 0 8px;
  font-size: clamp(1.8rem, 3vw, 2.5rem);
  line-height: 1.2;
}

.lead {
  margin: 0;
  color: var(--ink-soft);
}

.meta {
  margin-top: 14px;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
}

.meta div {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 10px;
  background: #fcfaf6;
}

.meta dt {
  margin: 0;
  font-size: 0.76rem;
  text-transform: uppercase;
  color: var(--ink-soft);
  letter-spacing: 0.05em;
}

.meta dd {
  margin: 5px 0 0;
  font-weight: 700;
}

.toc {
  margin-top: 20px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: #fdfbf7;
  padding: 14px 16px;
}

.toc h2 {
  margin: 0 0 8px;
  font-size: 1.05rem;
}

.toc ul {
  margin: 0;
  padding-left: 18px;
}

.toc a {
  color: var(--accent-dark);
  text-decoration: none;
}

.toc a:hover {
  text-decoration: underline;
}

section {
  margin-top: 26px;
}

section h2 {
  margin: 0 0 10px;
  font-size: 1.35rem;
}

section h3 {
  margin: 18px 0 8px;
  font-size: 1.05rem;
}

p,
li {
  color: #263445;
}

code,
kbd {
  font-family: "JetBrains Mono", "Consolas", monospace;
  background: #f2ecdf;
  border: 1px solid #e3d7c2;
  padding: 1px 6px;
  border-radius: 6px;
  font-size: 0.93em;
}

pre {
  margin: 0;
  overflow-x: auto;
  border-radius: 12px;
  border: 1px solid #243042;
  background: var(--code);
  color: #e5ebf5;
  padding: 12px 14px;
}

pre code {
  background: transparent;
  border: 0;
  padding: 0;
  color: inherit;
}

.box {
  margin: 12px 0;
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: 10px;
  padding: 10px 12px;
  background: #fbf8f1;
}

.def {
  background: var(--note);
  border-left-color: #2563eb;
}

.thm {
  background: var(--warn);
  border-left-color: #d97706;
}

.tip {
  background: var(--ok);
  border-left-color: #1f9d61;
}

.warning {
  background: #fff0f0;
  border-left-color: #dc2626;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 10px 0;
}

th,
td {
  border: 1px solid var(--border);
  padding: 8px 9px;
  text-align: left;
}

th {
  background: #f3ecdf;
}

.exam-min {
  margin-top: 30px;
  padding: 14px;
  border-radius: 12px;
  border: 1px dashed #c3b89f;
  background: #fbf6eb;
}

.exam-min h2 {
  margin-top: 0;
}

.footer-note {
  margin-top: 26px;
  padding-top: 14px;
  border-top: 1px solid var(--border);
  color: var(--ink-soft);
}

.footer-note a {
  color: var(--accent-dark);
  font-weight: 700;
  text-decoration: none;
}

.footer-note a:hover {
  text-decoration: underline;
}

@media (max-width: 860px) {
  .meta {
    grid-template-columns: 1fr;
  }

  article {
    padding: 18px;
  }
}