* {
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Arial, sans-serif;
  line-height: 1.6;
  max-width: 980px;
  margin: 0 auto;
  padding: 24px;
  color: #1f2937;
  background: #f9fafb;
}

h1, h2, h3 {
  color: #111827;
}

a {
  color: #1d4ed8;
}

a:hover {
  text-decoration: underline;
}

.site-header {
  margin-bottom: 24px;
}

.site-header .subtitle {
  color: #4b5563;
  margin-top: 4px;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 16px 0 24px;
}

.nav a {
  display: inline-block;
  padding: 6px 14px;
  border-radius: 999px;
  background: #ffffff;
  border: 1px solid #e5e7eb;
  text-decoration: none;
  font-size: 14px;
  color: #374151;
}

.nav a:hover {
  background: #eff6ff;
  border-color: #bfdbfe;
  color: #1d4ed8;
}

.nav a.active {
  background: #1d4ed8;
  border-color: #1d4ed8;
  color: #ffffff;
}

.card {
  background: #ffffff;
  border: 1px solid #e5e7eb;
  border-radius: 10px;
  padding: 16px 20px;
  margin-bottom: 16px;
}

.card h2 {
  margin-top: 0;
}

.tag {
  display: inline-block;
  background: #e0f2fe;
  color: #075985;
  padding: 3px 10px;
  border-radius: 999px;
  font-size: 12px;
  margin-right: 6px;
  margin-bottom: 6px;
}

.tag.warn {
  background: #fef3c7;
  color: #92400e;
}

.resource-link {
  display: block;
  margin: 8px 0;
  padding: 10px 12px;
  background: #f8fafc;
  border: 1px solid #e5e7eb;
  border-radius: 8px;
  text-decoration: none;
  color: #1d4ed8;
}

.resource-link:hover {
  background: #eff6ff;
  border-color: #bfdbfe;
}

.resource-link .label {
  display: block;
  font-weight: 600;
  color: #111827;
}

.resource-link .url {
  display: block;
  font-size: 13px;
  color: #6b7280;
  word-break: break-all;
}

code {
  background: #f3f4f6;
  padding: 1px 5px;
  border-radius: 4px;
  font-size: 0.92em;
}

ul {
  margin-top: 8px;
}

.day-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}

.day-card {
  background: #ffffff;
  border: 1px solid #e5e7eb;
  border-radius: 10px;
  padding: 20px;
  text-decoration: none;
  color: inherit;
  transition: box-shadow 0.15s ease, border-color 0.15s ease;
}

.day-card:hover {
  border-color: #93c5fd;
  box-shadow: 0 4px 12px rgba(29, 78, 216, 0.08);
}

.day-card h2 {
  margin: 0 0 8px;
  color: #1d4ed8;
}

.day-card p {
  margin: 0;
  color: #4b5563;
  font-size: 14px;
}

.footer {
  margin-top: 32px;
  padding-top: 16px;
  border-top: 1px solid #e5e7eb;
  font-size: 14px;
  color: #6b7280;
}

.concept {
  background: #f0f9ff;
  border-left: 4px solid #38bdf8;
  padding: 12px 16px;
  margin: 12px 0;
  border-radius: 0 8px 8px 0;
}

.concept h3 {
  margin: 0 0 6px;
  font-size: 1rem;
  color: #0c4a6e;
}

.concept p {
  margin: 0 0 8px;
}

.concept p:last-child {
  margin-bottom: 0;
}

.analogy {
  font-style: italic;
  color: #4b5563;
  margin: 6px 0 0;
}

.tool-compare {
  width: 100%;
  border-collapse: collapse;
  margin: 12px 0;
  font-size: 14px;
}

.tool-compare th,
.tool-compare td {
  border: 1px solid #e5e7eb;
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
}

.tool-compare th {
  background: #f8fafc;
  color: #111827;
}

.tool-compare .course-tool {
  background: #eff6ff;
}

.lead {
  font-size: 1.05rem;
  color: #374151;
}

.section-note {
  font-size: 14px;
  color: #6b7280;
  margin-bottom: 12px;
}