:root {
  --red: #d01012;
  --yellow: #f5cd2f;
  --blue: #0055bf;
  --green: #237841;
  --ink: #1c1c1c;
  --paper: #fff8e7;
  --card: #ffffff;
  --muted: #5a5a5a;
  --shadow: 0 8px 0 rgba(0, 0, 0, 0.16);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  min-height: 100%;
  color: var(--ink);
  font-family: "Microsoft JhengHei", "PingFang TC", "Noto Sans TC", sans-serif;
  background: #3b9ae1;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.studs {
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image: radial-gradient(circle at 12px 12px, rgba(255, 255, 255, 0.18) 7px, transparent 8px);
  background-size: 36px 36px;
  z-index: 0;
}

.topbar, main, .foot { position: relative; z-index: 1; }

.topbar, .foot {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 16px;
}

.topbar {
  background: #ffd54a;
  border-bottom: 6px solid #e0a800;
}

.foot {
  margin-top: auto;
  justify-content: center;
  flex-wrap: wrap;
  background: rgba(0, 40, 80, 0.25);
  color: #fff;
  font-size: 13px;
}

.brand-text {
  margin: 0;
  font-family: "Segoe UI", "Helvetica Neue", "Microsoft JhengHei", sans-serif;
  font-weight: 800;
  color: #8a09ef;
  line-height: 1.3;
  white-space: nowrap;
}

.brand-text-bar {
  font-size: 14px;
}

.brand-text-cover {
  margin: 0 0 14px;
  font-size: 22px;
  letter-spacing: 0.04em;
}

.brand-text-foot {
  font-size: 13px;
  color: #e8d2ff;
}

.disclaimer {
  margin: 12px 0 0;
  font-size: 13px;
  font-weight: 700;
  color: #7a1f1f;
  line-height: 1.5;
}

.foot .disclaimer {
  margin: 0;
  color: #fff;
}

.brand {
  flex: 1;
  margin: 0;
  text-align: center;
  font-size: 1.2rem;
}

.page-label {
  font-weight: 800;
  min-width: 6rem;
  text-align: right;
}

.btn {
  border: 0;
  border-radius: 12px;
  padding: 0.55rem 0.95rem;
  font: inherit;
  font-weight: 800;
  cursor: pointer;
  box-shadow: var(--shadow);
}

.btn:active { transform: translateY(2px); box-shadow: 0 4px 0 rgba(0, 0, 0, 0.16); }
.btn:disabled { opacity: 0.45; cursor: default; box-shadow: none; }

.btn-ghost { background: #fff; color: var(--ink); }
.btn-primary { background: var(--red); color: #fff; }
.btn-blue { background: var(--blue); color: #fff; }
.btn-green { background: var(--green); color: #fff; }
.btn-yellow { background: var(--yellow); color: var(--ink); }
.btn-xl { font-size: 1.15rem; padding: 0.8rem 1.6rem; }

.view { display: none; padding: 22px 16px 28px; }
.view.active { display: block; }

.cover-card, .panel {
  max-width: 920px;
  margin: 0 auto;
  background: var(--paper);
  border-radius: 24px;
  box-shadow: var(--shadow);
  padding: 28px 24px;
}

.cover-card { text-align: center; }
.cover-kicker { margin: 0; color: var(--blue); font-weight: 800; }
.cover-title { margin: 8px 0 0; font-size: 2.2rem; }
.cover-sub { color: var(--muted); }
.cover-hero {
  width: min(100%, 420px);
  height: 220px;
  object-fit: cover;
  border-radius: 18px;
  border: 6px solid #fff;
  box-shadow: var(--shadow);
}
.cover-stats {
  display: flex;
  justify-content: center;
  gap: 18px;
  flex-wrap: wrap;
  margin: 16px 0 20px;
}
.cover-stats span {
  background: #fff;
  border-radius: 999px;
  padding: 6px 14px;
  font-weight: 800;
}

.toc-head, .quiz-head {
  max-width: 1100px;
  margin: 0 auto 16px;
  background: var(--paper);
  border-radius: 20px;
  padding: 16px 18px;
  box-shadow: var(--shadow);
}

.toc-head h2, .quiz-head h2 { margin: 0 0 8px; }
.muted { color: var(--muted); }

#search {
  width: 100%;
  margin-top: 10px;
  padding: 10px 12px;
  border: 3px solid #e0a800;
  border-radius: 12px;
  font: inherit;
}

.unit-list { max-width: 1100px; margin: 0 auto; display: grid; gap: 16px; }

.unit {
  background: var(--paper);
  border-radius: 20px;
  padding: 14px;
  box-shadow: var(--shadow);
}

.unit h3 { margin: 0 0 4px; }
.unit .blurb { margin: 0 0 10px; color: var(--muted); font-size: 14px; }

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 10px;
}

.card {
  border: 0;
  background: #fff;
  border-radius: 14px;
  overflow: hidden;
  cursor: pointer;
  text-align: left;
  box-shadow: 0 4px 0 rgba(0, 0, 0, 0.12);
  padding: 0;
  font: inherit;
}

.card img { width: 100%; height: 96px; object-fit: cover; display: block; }
.card .name { margin: 0; padding: 8px; font-weight: 800; }
.card.seen .name { color: var(--green); }

.lesson {
  max-width: 1180px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 16px;
}

.lesson-art, .lesson-card {
  background: var(--paper);
  border-radius: 20px;
  box-shadow: var(--shadow);
  padding: 14px;
}

.lesson-art img {
  width: 100%;
  max-height: 68vh;
  object-fit: contain;
  background: #fff;
  border-radius: 14px;
}

.kicker { margin: 0; color: var(--blue); font-weight: 800; }
.lesson-card h2 { margin: 6px 0 10px; font-size: 2rem; }
.hidden-name { filter: blur(8px); user-select: none; }

.box {
  background: #fff;
  border-radius: 14px;
  padding: 10px 12px;
  margin: 0 0 10px;
}

.box dt { font-weight: 800; color: var(--red); margin: 0 0 4px; }
.box dd { margin: 0; }
.box.hidden { display: none; }

.lesson-actions, .pager {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
}

.pager {
  max-width: 1180px;
  margin: 16px auto 0;
  justify-content: space-between;
}

.quiz-card {
  max-width: 820px;
  margin: 0 auto;
  background: var(--paper);
  border-radius: 24px;
  box-shadow: var(--shadow);
  padding: 22px;
}

.quiz-example {
  font-size: 1.35rem;
  font-weight: 800;
  background: #fff;
  border-radius: 16px;
  padding: 16px;
  margin: 12px 0 16px;
}

.choices { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.choice {
  background: #fff;
  border: 3px solid #e0a800;
  border-radius: 14px;
  padding: 12px;
  font-weight: 800;
  cursor: pointer;
}
.choice.correct { background: #d7f5df; border-color: var(--green); }
.choice.wrong { background: #ffd6d6; border-color: var(--red); }

.feedback { min-height: 1.6em; font-weight: 800; }
.score { font-weight: 800; color: var(--blue); }

@media (max-width: 860px) {
  .lesson { grid-template-columns: 1fr; }
  .choices { grid-template-columns: 1fr; }
  .page-label { display: none; }
  .cover-title { font-size: 1.7rem; }
}