/* ============================================================
   S.3 Maths Answer Finder — styles
   Reference: white card, blue title, numbered step labels,
   big blue button, yellow highlight for final answer
   ============================================================ */

/* ---------- Reset & base ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue",
               Arial, "Noto Sans TC", sans-serif;
  background: #f0f2f5;
  min-height: 100vh;
  padding: 24px 16px 48px;
  color: #1a1a2e;
  font-size: 15px;
  line-height: 1.6;
}

/* ---------- Page wrapper ---------- */
.page-wrap {
  max-width: 600px;
  margin: 0 auto;
}

/* ---------- Card ---------- */
.card {
  background: #ffffff;
  border-radius: 16px;
  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.10), 0 1px 4px rgba(0, 0, 0, 0.06);
  padding: 28px 24px 32px;
}

/* ---------- Card title ---------- */
.card-title {
  text-align: center;
  margin-bottom: 28px;
}

.card-title h1 {
  font-size: 1.45rem;
  font-weight: 800;
  color: #1a56db;
  letter-spacing: -0.01em;
  line-height: 1.3;
}

/* ---------- Form groups ---------- */
.form-group {
  margin-bottom: 20px;
}

/* ---------- Step labels ---------- */
.step-label {
  font-weight: 700;
  font-size: 0.875rem;
  color: #374151;
  margin-bottom: 10px;
  letter-spacing: 0.01em;
}

/* ---------- Section tabs ---------- */
.section-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tab {
  padding: 8px 16px;
  border-radius: 20px;
  border: 1.5px solid #d1d5db;
  background: #f9fafb;
  color: #374151;
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s, color 0.15s, box-shadow 0.15s;
  outline: none;
  -webkit-tap-highlight-color: transparent;
}

.tab:hover {
  border-color: #1a56db;
  color: #1a56db;
  background: #eff6ff;
}

.tab.active {
  background: #1a56db;
  border-color: #1a56db;
  color: #ffffff;
  box-shadow: 0 2px 8px rgba(26, 86, 219, 0.30);
}

/* UT tab accent */
.tab-ut {
  border-color: #f59e0b;
  color: #92400e;
  background: #fffbeb;
}

.tab-ut:hover {
  background: #fef3c7;
  border-color: #d97706;
  color: #78350f;
}

.tab-ut.active {
  background: #f59e0b;
  border-color: #f59e0b;
  color: #ffffff;
  box-shadow: 0 2px 8px rgba(245, 158, 11, 0.35);
}

/* ---------- Select wrapper ---------- */
.select-wrap {
  position: relative;
}

.select-wrap::after {
  content: "▾";
  position: absolute;
  right: 14px;
  top: 50%;
  transform: translateY(-50%);
  color: #6b7280;
  pointer-events: none;
  font-size: 0.9rem;
}

select {
  width: 100%;
  appearance: none;
  -webkit-appearance: none;
  background: #ffffff;
  border: 1.5px solid #d1d5db;
  border-radius: 10px;
  padding: 11px 40px 11px 14px;
  font-size: 0.9rem;
  color: #1a1a2e;
  cursor: pointer;
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
  font-family: inherit;
}

select:focus {
  border-color: #1a56db;
  box-shadow: 0 0 0 3px rgba(26, 86, 219, 0.12);
}

/* ---------- CTA button ---------- */
.btn-check {
  display: block;
  width: 100%;
  padding: 14px 20px;
  margin-top: 8px;
  background: #1a56db;
  color: #ffffff;
  font-size: 1rem;
  font-weight: 700;
  border: none;
  border-radius: 12px;
  cursor: pointer;
  letter-spacing: 0.01em;
  transition: background 0.15s, box-shadow 0.15s, transform 0.1s;
  -webkit-tap-highlight-color: transparent;
}

.btn-check:hover {
  background: #1648c0;
  box-shadow: 0 4px 16px rgba(26, 86, 219, 0.35);
}

.btn-check:active {
  transform: scale(0.98);
  background: #1340a8;
}

/* ---------- Answer panel ---------- */
.answer-panel {
  margin-top: 24px;
  border-top: 2px solid #e5e7eb;
  padding-top: 20px;
  animation: fadeIn 0.25s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* Answer header (question label) */
.answer-header {
  font-size: 0.95rem;
  font-weight: 700;
  color: #1a56db;
  margin-bottom: 14px;
}

/* ---------- Steps container ---------- */
#steps-container {
  margin-bottom: 16px;
}

/* Part label: (a), (b), etc. */
.part-block {
  margin-bottom: 18px;
}

.part-label {
  font-weight: 700;
  font-size: 0.875rem;
  color: #374151;
  margin-bottom: 6px;
}

/* Working steps list */
.steps-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.steps-list li {
  position: relative;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: baseline;
  gap: 4px 8px;
  padding: 5px 0 5px 28px;
  font-size: 0.875rem;
  color: #374151;
  border-bottom: 1px solid #f3f4f6;
  line-height: 1.55;
}

.steps-list li:last-child {
  border-bottom: none;
}

/* Step counter bubble */
.steps-list li::before {
  content: attr(data-n);
  position: absolute;
  left: 0;
  top: 7px;
  width: 18px;
  height: 18px;
  background: #dbeafe;
  color: #1a56db;
  border-radius: 50%;
  font-size: 0.7rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  line-height: 1;
  text-align: center;
}

/* Working text (left side) */
.step-work {
  flex: 1 1 auto;
  font-family: inherit;
  white-space: pre-wrap;
}

/* Reason text (right side, italic) */
.step-reason {
  flex: 0 1 auto;
  color: #6b7280;
  font-style: italic;
  font-size: 0.8rem;
  white-space: normal;
  word-break: break-word;
  padding-left: 10px;
  text-align: right;
}

/* MCQ / short step (no numbering when single step) */
.steps-list.single-step li {
  padding-left: 0;
}
.steps-list.single-step li::before {
  display: none;
}

/* ---------- Final answer (yellow highlight) ---------- */
.final-answer {
  background: #fef08a;
  border-radius: 8px;
  padding: 10px 14px;
  font-size: 0.9rem;
  font-weight: 700;
  color: #713f12;
  line-height: 1.5;
  border: 1px solid #fde047;
}

.part-final-answer {
  background: #fef08a;
  border-radius: 6px;
  padding: 7px 12px;
  font-size: 0.875rem;
  font-weight: 700;
  color: #713f12;
  margin-top: 6px;
  border: 1px solid #fde047;
}

/* MCQ pill answer */
.mcq-answer {
  display: inline-block;
  background: #fef08a;
  border: 1px solid #fde047;
  color: #713f12;
  font-weight: 800;
  font-size: 1.1rem;
  padding: 6px 18px;
  border-radius: 8px;
}

/* ---------- Stacked fractions ---------- */
.frac {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  vertical-align: middle;
  margin: 0 2px;
  font-size: 0.85em;
  line-height: 1.2;
}
.frac .num {
  border-bottom: 1.5px solid currentColor;
  padding: 0 3px 1px;
  text-align: center;
  white-space: nowrap;
}
.frac .den {
  padding: 1px 3px 0;
  text-align: center;
  white-space: nowrap;
}

/* ---------- Footer ---------- */
footer {
  text-align: center;
  margin-top: 24px;
  padding-bottom: 8px;
}

footer a {
  font-size: 0.75rem;
  color: #9ca3af;
  text-decoration: none;
}

footer a:hover {
  color: #6b7280;
  text-decoration: underline;
}

/* ---------- Responsive tweaks ---------- */
@media (max-width: 400px) {
  .card { padding: 22px 16px 28px; }
  .card-title h1 { font-size: 1.2rem; }
  .tab { padding: 7px 13px; font-size: 0.8rem; }
}