/* ===== Exam Prep — Dedicated Styles ===== */

/* ── Difficulty Colors ─────────────────────────────────────────── */
:root {
  --diff-c: #16a34a;
  --diff-c-bg: rgba(22,163,74,0.08);
  --diff-c-border: rgba(22,163,74,0.25);
  --diff-b: #2563eb;
  --diff-b-bg: rgba(37,99,235,0.08);
  --diff-b-border: rgba(37,99,235,0.25);
  --diff-a: #9333ea;
  --diff-a-bg: rgba(147,51,234,0.08);
  --diff-a-border: rgba(147,51,234,0.25);
}

/* ── Index: Difficulty Cards ───────────────────────────────────── */
.diff-grid {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 1rem;
  margin-top: 1.5rem;
}
.diff-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 2rem 1rem;
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  cursor: pointer;
  transition: all .3s;
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow);
}
.diff-card:hover {
  /* removed translateY per DESIGN.md */
  box-shadow: var(--shadow-md);
}
.diff-card.selected {
  /* removed translateY per DESIGN.md */
  box-shadow: var(--shadow-md);
}
.diff-card .diff-icon { font-size: 2.5rem; margin-bottom: .5rem; }
.diff-card .diff-label { font-size: 1.2rem; font-weight: 700; }
.diff-card .diff-desc { font-size: .82rem; color: var(--text-secondary); margin-top: .25rem; }

.diff-card[data-diff="c"] { border-color: var(--diff-c-border); }
.diff-card[data-diff="c"]:hover,
.diff-card[data-diff="c"].selected { border-color: var(--diff-c); background: var(--diff-c-bg); }
.diff-card[data-diff="c"] .diff-label { color: var(--diff-c); }

.diff-card[data-diff="b"] { border-color: var(--diff-b-border); }
.diff-card[data-diff="b"]:hover,
.diff-card[data-diff="b"].selected { border-color: var(--diff-b); background: var(--diff-b-bg); }
.diff-card[data-diff="b"] .diff-label { color: var(--diff-b); }

.diff-card[data-diff="a"] { border-color: var(--diff-a-border); }
.diff-card[data-diff="a"]:hover,
.diff-card[data-diff="a"].selected { border-color: var(--diff-a); background: var(--diff-a-bg); }
.diff-card[data-diff="a"] .diff-label { color: var(--diff-a); }

/* ── Index: Book Grid ──────────────────────────────────────────── */
.book-section { margin-top: 2rem; }
.book-section h3 {
  font-size: 1rem;
  color: var(--text-secondary);
  margin-bottom: .75rem;
}
.book-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: .75rem;
}
.book-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 1.1rem .75rem;
  background: var(--bg-card);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-family: inherit;
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  transition: all .2s;
}
.book-btn:hover {
  border-color: var(--accent);
  background: var(--accent-light, #EFF6FF);
  /* removed translateY per DESIGN.md */
}
.book-btn .book-num { font-size: 1.5rem; font-weight: 800; }
.book-btn .book-info {
  font-size: .75rem;
  color: var(--text-muted);
  font-weight: 400;
  margin-top: .25rem;
}
.book-btn.disabled {
  opacity: .4;
  cursor: not-allowed;
  pointer-events: none;
}

/* ── Index: Year Grid ─────────────────────────────────────────── */
.year-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: .6rem;
}
.year-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: .8rem .5rem;
  background: var(--bg-card);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-family: inherit;
  transition: all .2s;
  color: inherit;
}
.year-btn:hover {
  border-color: var(--accent);
  background: var(--accent-light, #EFF6FF);
  /* removed translateY per DESIGN.md */
  box-shadow: var(--shadow);
}
.year-btn .year-num { font-size: 1.15rem; font-weight: 700; color: var(--accent); }
.year-btn .year-label { font-size: .72rem; color: var(--text-muted); margin-top: .1rem; }

@media (max-width: 480px) {
  .year-grid { grid-template-columns: repeat(4, 1fr); }
}

/* ── Practice: Concept Tag ─────────────────────────────────────── */
.concept-tag {
  display: inline-block;
  padding: .2rem .6rem;
  background: var(--accent-light, #EFF6FF);
  color: var(--accent);
  border-radius: 4px;
  font-size: .78rem;
  font-weight: 600;
  margin-right: .5rem;
}
.pass-rate-tag {
  display: inline-block;
  padding: .2rem .6rem;
  border-radius: 4px;
  font-size: .78rem;
  font-weight: 600;
}
.pass-rate-tag.high { background: rgba(22,163,74,0.08); color: var(--accent-green); }
.pass-rate-tag.mid { background: rgba(217,119,6,0.08); color: var(--accent-yellow); }
.pass-rate-tag.low { background: rgba(220,38,38,0.08); color: var(--accent-red); }

.q-tags {
  display: flex;
  flex-wrap: wrap;
  gap: .4rem;
  margin-top: 1rem;
  padding-top: .75rem;
  border-top: 1px solid var(--border);
}

/* ── Practice: Difficulty Badge ────────────────────────────────── */
.diff-badge {
  display: inline-block;
  padding: .15rem .55rem;
  border-radius: 4px;
  font-size: .8rem;
  font-weight: 700;
}
.diff-badge.diff-c { background: var(--diff-c-bg); color: var(--diff-c); border: 1px solid var(--diff-c-border); }
.diff-badge.diff-b { background: var(--diff-b-bg); color: var(--diff-b); border: 1px solid var(--diff-b-border); }
.diff-badge.diff-a { background: var(--diff-a-bg); color: var(--diff-a); border: 1px solid var(--diff-a-border); }

/* ── Practice: Solution Steps ──────────────────────────────────── */
.exp-body strong {
  color: var(--accent-yellow);
}
.exp-body p {
  margin-bottom: .5rem;
}

/* ── 觀念筆記 & 先備觀念 ── */
.concept-note, .prereq-note {
  margin-top: .75rem;
  padding: .6rem .8rem;
  border-radius: 8px;
  font-size: .92em;
  line-height: 1.6;
}
.concept-note {
  background: rgba(59, 130, 246, 0.08);
  border-left: 3px solid #3b82f6;
}
.prereq-note {
  background: rgba(234, 179, 8, 0.08);
  border-left: 3px solid #eab308;
}
.cn-label, .pn-label {
  display: block;
  font-weight: 700;
  margin-bottom: .25rem;
}
.cn-label { color: #3b82f6; }
.pn-label { color: #d97706; }

/* ── Practice: Figure from image file ──────────────────────────── */
.q-figure-img {
  text-align: center;
  margin-bottom: 1.25rem;
  padding: .75rem;
  background: var(--bg-card2);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
}
.q-figure-img img {
  max-width: 100%;
  max-height: 300px;
  height: auto;
  border-radius: 6px;
}

/* ── Practice: TikZ rendered as KaTeX ──────────────────────────── */
.q-tikz-figure {
  text-align: center;
  margin-bottom: 1.25rem;
  padding: .5rem .75rem;
  background: var(--bg-card2);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
}

/* ── Practice: Nav row with prev button ────────────────────────── */
.nav-row-exam {
  display: flex;
  justify-content: space-between;
  margin-top: 1.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
}

/* ── Shake animation for wrong answer ──────────────────────────── */
@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20% { transform: translateX(-6px); }
  40% { transform: translateX(6px); }
  60% { transform: translateX(-4px); }
  80% { transform: translateX(4px); }
}
.option-btn.wrong {
  animation: shake .4s ease;
}

/* ── Index: Difficulty Tag Grid (5 buttons) ──────────────────── */
.diff-tag-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: .6rem;
}
.diff-tag-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: .8rem .5rem;
  background: var(--bg-card);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  text-decoration: none;
  color: inherit;
  transition: all .2s;
}
.diff-tag-btn:hover {
  /* removed translateY per DESIGN.md */
  box-shadow: var(--shadow);
}
.diff-tag-btn .diff-tag-emoji { font-size: 1.5rem; margin-bottom: .25rem; }
.diff-tag-btn .diff-tag-name { font-size: .85rem; font-weight: 600; }
.diff-tag-btn[data-tag="gift"] { border-color: rgba(22,163,74,0.3); }
.diff-tag-btn[data-tag="gift"]:hover { background: rgba(22,163,74,0.06); border-color: #16a34a; }
.diff-tag-btn[data-tag="gift"] .diff-tag-name { color: #16a34a; }
.diff-tag-btn[data-tag="basic"] { border-color: rgba(37,99,235,0.3); }
.diff-tag-btn[data-tag="basic"]:hover { background: rgba(37,99,235,0.06); border-color: #2563eb; }
.diff-tag-btn[data-tag="basic"] .diff-tag-name { color: #2563eb; }
.diff-tag-btn[data-tag="mid"] { border-color: rgba(217,119,6,0.3); }
.diff-tag-btn[data-tag="mid"]:hover { background: rgba(217,119,6,0.06); border-color: #d97706; }
.diff-tag-btn[data-tag="mid"] .diff-tag-name { color: #d97706; }
.diff-tag-btn[data-tag="key"] { border-color: rgba(147,51,234,0.3); }
.diff-tag-btn[data-tag="key"]:hover { background: rgba(147,51,234,0.06); border-color: #9333ea; }
.diff-tag-btn[data-tag="key"] .diff-tag-name { color: #9333ea; }
.diff-tag-btn[data-tag="boss"] { border-color: rgba(220,38,38,0.3); }
.diff-tag-btn[data-tag="boss"]:hover { background: rgba(220,38,38,0.06); border-color: #dc2626; }
.diff-tag-btn[data-tag="boss"] .diff-tag-name { color: #dc2626; }

/* ── Responsive ────────────────────────────────────────────────── */
@media (max-width: 600px) {
  .diff-grid { grid-template-columns: 1fr; gap: .75rem; }
  .diff-card { padding: 1.25rem 1rem; flex-direction: row; gap: 1rem; }
  .diff-card .diff-icon { font-size: 2rem; margin-bottom: 0; }
  .book-grid { grid-template-columns: repeat(3, 1fr); }
}
@media (max-width: 480px) {
  .book-grid { grid-template-columns: repeat(2, 1fr); }
}