:root {
  /* 淡绿背景 + 苹果风层次 */
  --bg: #e2efe5;            /* 页面淡绿底 */
  --bg-grad-1: #dcefe2;
  --bg-grad-2: #e6f1e9;
  --surface: #ffffff;       /* 卡片/面板表面 */
  --surface-soft: #f6faf7;  /* 次级表面 */
  --fg: #1f2a24;
  --muted: #8a958e;
  --line: rgba(60, 90, 70, 0.10);
  --accent: #2f9e6f;        /* 主色：克制的绿 */
  --accent-soft: #e3f3ea;
  --correct: #d8000c;       /* 复习正确答案高亮：红 */
  --right: #1a9c5b;         /* 测试答对：绿 */
  --wrong: #d8000c;         /* 测试答错：红 */
  /* 苹果风柔和阴影 */
  --shadow-sm: 0 1px 2px rgba(30, 60, 40, 0.04), 0 1px 3px rgba(30, 60, 40, 0.06);
  --shadow-md: 0 2px 6px rgba(30, 60, 40, 0.05), 0 8px 24px rgba(30, 60, 40, 0.08);
  --shadow-lg: 0 4px 12px rgba(30, 60, 40, 0.06), 0 16px 40px rgba(30, 60, 40, 0.10);
  --radius: 16px;
  --radius-lg: 22px;
}

* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }

html, body {
  margin: 0;
  padding: 0;
  background: linear-gradient(160deg, var(--bg-grad-1) 0%, var(--bg-grad-2) 100%);
  background-attachment: fixed;
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

#app {
  max-width: 760px;
  margin: 0 auto;
  padding: 28px 18px 64px;
  min-height: 100vh;
}

.hidden { display: none !important; }

/* —— 首页 —— */
.title {
  text-align: center;
  font-size: 2.7rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  margin: 30px 0 8px;
  color: #213027;
}
.subtitle {
  text-align: center;
  color: var(--accent);
  font-size: 0.95rem;
  margin: 0 0 40px;
  letter-spacing: 0.02em;
}
.section-label {
  font-size: 1.05rem;
  font-weight: 600;
  margin: 24px 0 16px;
  color: #3a463f;
}

.material-list { display: flex; flex-direction: column; gap: 14px; }
.material-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 20px;
  cursor: pointer;
  background: var(--surface);
  box-shadow: var(--shadow-sm);
  transition: transform .18s cubic-bezier(.2,.7,.3,1), box-shadow .18s, border-color .18s;
}
.material-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: rgba(47,158,111,0.25); }
.material-card:active { transform: translateY(-1px) scale(0.995); }
.material-card .mc-name { font-size: 1.12rem; font-weight: 600; color: #243029; }
.material-card .mc-meta { color: var(--muted); font-size: 0.85rem; margin-top: 4px; }
.material-card .progress-bar {
  height: 7px; background: #e8eee9; border-radius: 4px; margin-top: 12px; overflow: hidden;
}
.material-card .progress-fill {
  height: 100%; border-radius: 4px;
  background: linear-gradient(90deg, #43b787, #2f9e6f);
  width: 0; transition: width .4s ease;
}
.material-card .progress-text { font-size: 0.8rem; color: var(--muted); margin-top: 5px; }

.wrongbook-entry { margin-top: 32px; }
.wrongbook-card {
  border: 1px solid var(--line); border-radius: var(--radius); padding: 16px 20px;
  cursor: pointer; text-align: center; color: #3a463f;
  background: var(--surface-soft); box-shadow: var(--shadow-sm);
  transition: transform .18s, box-shadow .18s;
}
.wrongbook-card:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); }

/* —— 通用按钮 —— */
.back {
  background: none; border: none; color: var(--muted);
  font-size: 0.95rem; cursor: pointer; padding: 4px 0; margin-bottom: 16px;
}
.back:hover { color: var(--accent); }
.primary-btn {
  background: var(--accent); color: #fff; border: none; border-radius: 12px;
  padding: 13px 30px; font-size: 1rem; cursor: pointer; font-weight: 600;
  box-shadow: 0 4px 14px rgba(47,158,111,0.30);
  transition: transform .12s, box-shadow .12s, opacity .12s;
}
.primary-btn:hover { transform: translateY(-1px); box-shadow: 0 6px 18px rgba(47,158,111,0.36); }
.primary-btn:active { transform: translateY(0); opacity: .9; }
.mode-buttons { display: flex; gap: 16px; justify-content: center; margin-top: 12px; }
.mode-btn {
  flex: 1; max-width: 220px; padding: 26px 0; font-size: 1.22rem; font-weight: 600;
  border: 1px solid var(--line); border-radius: var(--radius-lg);
  background: var(--surface); cursor: pointer; color: #2a3530;
  box-shadow: var(--shadow-sm);
  transition: transform .18s cubic-bezier(.2,.7,.3,1), box-shadow .18s, border-color .18s;
}
.mode-btn:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: rgba(47,158,111,0.3); }

/* —— 模式选择页：垂直居中、略靠下 —— */
#mode { display: flex; flex-direction: column; }
.mode-center {
  flex: 1;
  display: flex; flex-direction: column; justify-content: center; align-items: center;
  min-height: 68vh;
  padding-top: 6vh; /* 略靠下，便于点击 */
}
.mode-title {
  font-size: 1.5rem; font-weight: 700; color: #243029;
  text-align: center; margin: 0 0 6px;
}
.mode-cheer {
  text-align: center; color: var(--accent); font-size: 1rem;
  margin: 0 0 30px; letter-spacing: 0.02em;
}
.mode-center .mode-buttons { width: 100%; }

/* —— 多题型滑块（新格式混合资料）—— */
.multi-sliders {
  margin: 10px 0; display: flex; flex-direction: column; gap: 18px;
  width: 100%; max-width: 480px;
}
.multi-row { text-align: left; }
.multi-label { display: block; font-size: 0.95rem; font-weight: 500; margin-bottom: 6px; color: #3a463f; }
.multi-slider { width: 100%; accent-color: var(--accent); }

/* —— section 列表 —— */
.section-list {
  display: flex; flex-direction: column; gap: 16px;
  margin-top: 10px; width: 100%; max-width: 480px;
}
.section-card {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 18px 20px;
  box-shadow: var(--shadow-sm);
  transition: transform .18s, box-shadow .18s;
}
.section-card:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); }
.section-card .sc-name { font-size: 1.1rem; font-weight: 600; color: #243029; }
.section-card .sc-meta { color: var(--muted); font-size: 0.85rem; margin: 4px 0 12px; }
.section-card .sc-btns { display: flex; gap: 10px; }
.sc-btn {
  flex: 1; padding: 10px 0; font-size: 0.95rem; font-weight: 600;
  border: 1px solid var(--line); border-radius: 10px;
  background: var(--surface-soft); cursor: pointer; color: #2a3530;
  transition: border-color .14s, transform .14s;
}
.sc-btn:hover { border-color: var(--accent); transform: translateY(-1px); }

/* —— 测试设置 —— */
.test-setup {
  margin-top: 30px; text-align: center;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius-lg); padding: 28px 24px; box-shadow: var(--shadow-md);
}
.slider-label { display: block; margin-bottom: 16px; font-size: 1.05rem; }
.slider-label .total-hint { color: var(--muted); font-size: 0.85rem; }
#count-slider {
  width: 100%; max-width: 440px; margin-bottom: 24px;
  accent-color: var(--accent); height: 4px;
}

/* —— 名词解释匹配 —— */
.option.term-option { font-size: 1.1rem; padding: 14px 18px; }
.option.term-option .opt-key { display: none; }

/* —— 问答布局 —— */
.quiz-body.essay-layout {
  display: flex; flex-direction: column; align-items: center;
  justify-content: flex-start; padding-top: 5vh;
  min-height: 55vh;
}
.essay-stem {
  font-size: 1.4rem; font-weight: 600; line-height: 1.8;
  color: #222c26; text-align: center; margin-bottom: 30px;
  max-width: 560px;
}
.show-answer-btn {
  margin-bottom: 24px; font-size: 1.05rem;
  padding: 14px 36px;
}
.essay-answer {
  max-width: 600px; text-align: left; background: var(--accent-soft);
  border: 1px solid rgba(47,158,111,0.18); border-radius: 14px;
  padding: 20px 22px; font-size: 1.05rem; color: #33493e; line-height: 1.9;
  margin: 0 auto;
}
.essay-answer.hidden { display: none !important; }

.remember-btn {
  margin-top: 20px; background: var(--accent); color: #fff; border: none;
  border-radius: 12px; padding: 12px 28px; font-size: 1rem; cursor: pointer;
  font-weight: 600; box-shadow: 0 4px 14px rgba(47,158,111,0.30);
}
.remember-btn.hidden { display: none !important; }

/* —— 答题页 —— */
.quiz-top {
  display: flex; align-items: center; justify-content: space-between;
  margin-bottom: 10px;
}
.quiz-top .back { margin-bottom: 0; }
.quiz-progress, .quiz-score { font-size: 0.85rem; color: var(--muted); }

.quiz-body {
  text-align: center;
  padding: 34px 22px;
  min-height: 50vh;
  display: flex; flex-direction: column; justify-content: center;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
}
.locate-hint { font-size: 0.78rem; color: #b3bdb6; margin-bottom: 12px; min-height: 1em; }
.question-stem {
  font-size: 1.5rem; font-weight: 600; line-height: 1.7; margin-bottom: 30px;
  color: #222c26;
}
.options { display: flex; flex-direction: column; gap: 14px; align-items: center; }
.option {
  width: 100%; max-width: 520px; padding: 16px 20px; font-size: 1.15rem;
  border: 1px solid var(--line); border-radius: 14px; cursor: pointer;
  background: var(--surface-soft); text-align: left; color: #2a3530;
  box-shadow: var(--shadow-sm);
  transition: transform .14s, box-shadow .14s, border-color .14s, background .14s;
}
.option:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); border-color: rgba(47,158,111,0.3); }
.option .opt-key { font-weight: 700; margin-right: 10px; color: var(--accent); }
.option.correct-highlight { color: var(--correct); border-color: var(--correct); font-weight: 600; background: #fff2f2; }
.option.correct-highlight .opt-key { color: var(--correct); }
.option.chosen-right { border-color: var(--right); background: #e7f8ee; color: var(--right); }
.option.chosen-wrong { border-color: var(--wrong); background: #fdebeb; color: var(--wrong); }
.option.show-correct { border-color: var(--right); color: var(--right); background: #e7f8ee; }
.option.selected { border-color: var(--accent); background: var(--accent-soft); }
.option.disabled { cursor: default; }
.option.disabled:hover { transform: none; box-shadow: var(--shadow-sm); }

.feedback { margin-top: 24px; font-size: 1.1rem; font-weight: 600; min-height: 1.4em; }
.feedback.right { color: var(--right); }
.feedback.wrong { color: var(--wrong); }

.explanation {
  margin: 16px auto 0; max-width: 560px; text-align: left;
  background: var(--accent-soft); border: 1px solid rgba(47,158,111,0.18); border-radius: 14px;
  padding: 15px 18px; font-size: 0.95rem; color: #33493e; line-height: 1.7;
}

.quiz-nav {
  display: flex; justify-content: space-between; gap: 12px;
  margin-top: 22px; align-items: center;
}
.nav-btn {
  flex: 1; padding: 13px 0; font-size: 1rem; border: 1px solid var(--line);
  border-radius: 12px; background: var(--surface); cursor: pointer; color: #33433b;
  box-shadow: var(--shadow-sm);
  transition: transform .14s, box-shadow .14s, border-color .14s;
}
.nav-btn:disabled { opacity: .4; cursor: default; box-shadow: none; }
.nav-btn:hover:not(:disabled) { transform: translateY(-2px); box-shadow: var(--shadow-md); border-color: rgba(47,158,111,0.3); }

/* —— 结果页 —— */
.result-score {
  text-align: center; font-size: 3.2rem; font-weight: 700; margin: 36px 0 12px;
  color: var(--accent);
}
.result-detail { text-align: center; color: var(--muted); margin-bottom: 32px; }

/* —— 响应式 —— */
@media (max-width: 600px) {
  .title { font-size: 2.2rem; }
  .question-stem { font-size: 1.28rem; }
  .option { font-size: 1.05rem; padding: 14px 16px; }
  .mode-btn { padding: 22px 0; font-size: 1.08rem; }
  .quiz-body { padding: 26px 14px; }
}