* {
  box-sizing: border-box;
}
:root {
  --navy: #16324f;
  --blue: #1769aa;
  --ink: #203040;
  --muted: #526b7f;
  --soft: #f5f9fc;
  --line: #dbe7ef;
  --accent: #d9edf2;
}
body {
  margin: 24px auto;
  max-width: 1200px;
  padding: 32px 36px 48px;
  background: #fff;
  color: var(--ink);
  font:
    16px/1.7 "Segoe UI",
    Tahoma,
    Verdana,
    sans-serif;
  box-shadow: 0 12px 48px #00142812;
  border-radius: 18px;
}
a {
  color: var(--blue);
}
h1,
h2,
h3 {
  color: var(--navy);
}
h1 {
  border-bottom: 3px solid var(--navy);
  padding-bottom: 0.6rem;
}
nav {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  padding: 10px 0 20px;
  border-bottom: 2px solid var(--line);
  margin-bottom: 30px;
}
nav a,
.button {
  background: var(--accent);
  color: var(--navy);
  padding: 7px 16px;
  border-radius: 20px;
  font-weight: 600;
  text-decoration: none;
}
.hero {
  text-align: center;
  padding: 20px 0 30px;
}
.hero h1 {
  border: 0;
}
.subtitle {
  color: var(--muted);
  font-size: 1.15rem;
}
.badge {
  display: inline-block;
  background: var(--navy);
  color: #fff;
  border-radius: 30px;
  padding: 5px 18px;
  font-weight: 600;
}
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
}
.card {
  display: flex;
  flex-direction: column;
  background: var(--soft);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 20px;
  min-height: 190px;
}
.card h2 {
  font-size: 1.15rem;
  border: 0;
  margin: 6px 0 12px;
  flex: 1;
}
.card p {
  color: var(--muted);
  font-size: 0.94rem;
}
.callout,
.practice,
.check {
  background: #eef7fa;
  border-left: 5px solid var(--navy);
  padding: 14px 20px;
  border-radius: 6px;
  margin: 20px 0;
}
.practice {
  background: #fff9e6;
  border-left-color: #f59e0b;
}
.check {
  background: #edf8f0;
  border-left-color: #2a7f6a;
}
details {
  background: #f5f7fa;
  border-left: 4px solid #1769aa;
  border-radius: 8px;
  padding: 8px 16px;
  margin: 14px 0;
}
details summary {
  cursor: pointer;
  font-weight: 600;
  color: var(--navy);
}
pre {
  background: #1e293b;
  color: #e2e8f0;
  padding: 16px;
  border-radius: 8px;
  overflow-x: auto;
}
code {
  font-family: Consolas, "Courier New", monospace;
}
li {
  margin: 0.35rem 0;
}
@media (max-width: 600px) {
  body {
    margin: 0;
    padding: 20px 18px 30px;
    border-radius: 0;
  }
  .grid {
    grid-template-columns: 1fr;
  }
}