body {
  font-family: system-ui, sans-serif;
  max-width: 800px;
  margin: 40px auto;
  padding: 0 20px;
  line-height: 1.6;
}
nav a {
  display: inline-block;
  margin-right: 15px;
  padding: 10px 16px;
  background: #2563eb;
  color: white;
  text-decoration: none;
  border-radius: 6px;
}
nav a.disabled {
  background: #cbd5e1;
  color: #64748b;
  cursor: default;
  pointer-events: none;
}
table {
  border-collapse: collapse;
  width: 100%;
  margin: 16px 0;
}
th, td {
  border: 1px solid #ddd;
  padding: 8px 12px;
  text-align: left;
}
th {
  background: #f1f5f9;
}
.example {
  background: #f8fafc;
  border-left: 4px solid #2563eb;
  padding: 12px 16px;
  margin: 12px 0;
  border-radius: 0 6px 6px 0;
}
.tip {
  background: #fffbeb;
  border-left: 4px solid #f59e0b;
  padding: 12px 16px;
  margin: 12px 0;
  border-radius: 0 6px 6px 0;
}
.domain-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin: 20px 0;
}
.domain-card {
  display: block;
  border: 1px solid #ddd;
  border-radius: 8px;
  padding: 16px;
  text-decoration: none;
  color: inherit;
}
.domain-card h2 { margin: 0 0 4px 0; font-size: 1.1em; color: #2563eb; }
.domain-card p { margin: 0; color: #555; }
.domain-card:not(.disabled):hover { border-color: #2563eb; background: #f8fafc; }
.domain-card.disabled { opacity: 0.55; }
.domain-card.disabled h2 { color: #64748b; }

.strategy-box {
  border: 1px solid #e2e8f0;
  border-radius: 8px;
  padding: 16px 20px;
  margin: 16px 0;
}
.strategy-box h3 { margin-top: 0; }

#calculator {
  width: 100%;
  height: 400px;
  border: 1px solid #ddd;
  border-radius: 8px;
  margin: 12px 0;
}

.question {
  border: 1px solid #ddd;
  border-radius: 8px;
  padding: 16px 20px;
  margin: 20px 0;
}
.question .prompt { font-weight: 600; margin-bottom: 12px; }
.question .choices { display: flex; flex-direction: column; gap: 8px; margin-bottom: 12px; }
.question label {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border: 1px solid #e2e8f0;
  border-radius: 6px;
  cursor: pointer;
}
.question label:hover { background: #f8fafc; }
.question label.correct-choice { background: #dcfce7; border-color: #22c55e; }
.question label.wrong-choice { background: #fee2e2; border-color: #ef4444; }
.check-btn {
  background: #2563eb;
  color: white;
  border: none;
  padding: 8px 16px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.95em;
}
.check-btn:hover { background: #1d4ed8; }
.explanation {
  display: none;
  margin-top: 14px;
  padding: 14px 16px;
  background: #f8fafc;
  border-left: 4px solid #2563eb;
  border-radius: 0 6px 6px 0;
}
.explanation.show { display: block; }
.explanation h4 { margin: 10px 0 4px 0; font-size: 0.95em; }
.explanation h4:first-child { margin-top: 0; }
.result-banner { font-weight: 600; margin-bottom: 8px; }
.result-banner.correct { color: #16a34a; }
.result-banner.wrong { color: #dc2626; }

/* Big section cards on the Math hub page */
.section-cards {
  display: flex;
  flex-direction: column;
  gap: 14px;
  margin: 24px 0;
}
.section-card {
  display: block;
  border: 2px solid #2563eb;
  border-radius: 10px;
  padding: 20px;
  text-decoration: none;
  color: inherit;
  background: #eff6ff;
}
.section-card h2 { margin: 0 0 6px 0; color: #1d4ed8; }
.section-card p { margin: 0; color: #334155; }

/* Desmos annotated breakdown (Study Guide) */
.d-line {
  font-family: "SF Mono", Consolas, monospace;
  font-size: 1.05em;
  padding: 10px 14px;
  background: #0f172a;
  color: #e2e8f0;
  border-radius: 6px;
  margin: 10px 0 6px 0;
  overflow-x: auto;
  white-space: nowrap;
}
.d-part { padding: 2px 5px; border-radius: 4px; margin: 0 1px; }
.d-c1 { background: #1d4ed8; }
.d-c2 { background: #16a34a; }
.d-c3 { background: #9333ea; }
.d-c4 { background: #ea580c; }
.d-legend { display: flex; flex-direction: column; gap: 6px; margin: 0 0 20px 0; }
.d-legend-item { display: flex; align-items: flex-start; gap: 8px; font-size: 0.95em; }
.d-swatch { width: 14px; height: 14px; border-radius: 4px; flex-shrink: 0; margin-top: 3px; }
.d-swatch.d-c1 { background: #1d4ed8; }
.d-swatch.d-c2 { background: #16a34a; }
.d-swatch.d-c3 { background: #9333ea; }
.d-swatch.d-c4 { background: #ea580c; }
.d-result {
  background: #f0fdf4;
  border-left: 4px solid #16a34a;
  padding: 10px 14px;
  border-radius: 0 6px 6px 0;
  margin-bottom: 20px;
}
.calculator-fallback {
  padding: 20px;
  text-align: center;
  border: 1px dashed #ccc;
  border-radius: 8px;
  color: #555;
}
.subtopic-section {
  border-top: 1px solid #e2e8f0;
  padding-top: 20px;
  margin-top: 28px;
}

/* Practice page topic selector */
.selector-domain {
  border: 1px solid #ddd;
  border-radius: 8px;
  padding: 14px 16px;
  margin: 12px 0;
}
.selector-domain.disabled { opacity: 0.5; }
.selector-domain h3 { margin: 0 0 8px 0; display: flex; align-items: center; gap: 8px; }
.selector-domain .subtopics { display: flex; flex-direction: column; gap: 6px; margin-left: 24px; }
.selector-domain label { display: flex; align-items: center; gap: 8px; cursor: pointer; }
.start-practice-btn {
  background: #16a34a;
  color: white;
  border: none;
  padding: 12px 24px;
  border-radius: 8px;
  font-size: 1.05em;
  cursor: pointer;
  margin: 16px 0;
}
.start-practice-btn:hover { background: #15803d; }
#practice-results { margin-top: 24px; }
.practice-empty-msg { color: #888; font-style: italic; }.domain {
  border: 1px solid #ddd;
  border-radius: 8px;
  padding: 16px;
  margin: 16px 0;
}
.domain a {
  display: inline-block;
  margin-right: 10px;
  margin-top: 8px;
  color: #2563eb;
  font-weight: 600;
}