/* ============================================================
   小学奥数 · 思维每日一练 —— 新中式风格
   水墨留白 · 细描线 · 东方排版节奏
   配色严格遵守视觉规范（勿替换色值）
   ============================================================ */

:root {
  --c-primary: #4c9a47;      /* 主色：竹青 */
  --c-accent: #ab5f96;       /* 辅助色：绛紫 */
  --c-cta: #44bb60;          /* 强调 / CTA */
  --c-bg: #f9fbf8;           /* 页面背景 */
  --c-card: #ffffff;         /* 卡片 / 表面 */
  --c-text: #1c2c1b;         /* 正文 */
  --c-muted: #5e7a5c;        /* 次要文字 */
  --c-line: #dce6db;         /* 描边 */

  --c-primary-soft: rgba(76, 154, 71, .08);
  --c-primary-mid: rgba(76, 154, 71, .16);
  --c-accent-soft: rgba(171, 95, 150, .09);
  --c-cta-soft: rgba(68, 187, 96, .12);

  --r: 4px;                                   /* 圆角 4px */
  --font-serif: 'Noto Serif SC', 'Songti SC', 'STSong', 'SimSun', Georgia, 'Times New Roman', serif;
  --font-sans: system-ui, -apple-system, 'PingFang SC', 'Microsoft YaHei', 'Segoe UI', Roboto, sans-serif;

  --shadow-card: 0 1px 2px rgba(28, 44, 27, .03), 0 8px 24px rgba(28, 44, 27, .05);
  --shadow-lift: 0 2px 4px rgba(28, 44, 27, .04), 0 16px 32px rgba(28, 44, 27, .08);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--c-bg);
  color: var(--c-text);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.9;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4 { font-family: var(--font-serif); font-weight: 700; line-height: 1.5; margin: 0; }

a { color: var(--c-primary); text-decoration: none; }
p { margin: 0 0 1em; }

:focus-visible { outline: 2px solid var(--c-primary); outline-offset: 2px; border-radius: var(--r); }

.wrap { max-width: 960px; margin: 0 auto; padding: 0 20px; }

.sr-only {
  position: absolute; width: 1px; height: 1px;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap;
}

/* ============ 顶栏 ============ */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(249, 251, 248, .92);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--c-line);
}

.header-inner {
  display: flex; align-items: center; justify-content: space-between;
  min-height: 68px; gap: 16px;
}

.brand { display: inline-flex; align-items: center; gap: 12px; color: inherit; }

.brand-seal {
  width: 40px; height: 40px; flex: 0 0 auto;
  display: grid; place-items: center;
  background: var(--c-primary); color: #fff;
  font-family: var(--font-serif); font-weight: 700; font-size: 20px;
  border-radius: var(--r);
  transform: rotate(-3deg);
  box-shadow: inset 0 0 0 2px rgba(255, 255, 255, .35), 0 2px 6px rgba(28, 44, 27, .18);
}

.brand-text { display: flex; flex-direction: column; line-height: 1.3; }
.brand-name { font-family: var(--font-serif); font-size: 18px; letter-spacing: 2px; font-weight: 700; }
.brand-sub { font-size: 11px; color: var(--c-muted); letter-spacing: 3px; }

.site-nav { display: flex; gap: 6px; }
.nav-link {
  padding: 8px 14px; font-size: 15px; color: var(--c-muted);
  border: 1px solid transparent; border-radius: var(--r);
  transition: color .2s, background .2s, border-color .2s;
}
.nav-link:hover { color: var(--c-primary); background: var(--c-primary-soft); }
.nav-link.active {
  color: var(--c-primary); background: var(--c-primary-soft);
  border-color: var(--c-primary); font-family: var(--font-serif); font-weight: 600;
}

/* ============ Hero（水墨留白） ============ */
.hero {
  position: relative; overflow: hidden;
  padding: 52px 0 44px;
  border-bottom: 1px solid var(--c-line);
  background:
    radial-gradient(1200px 300px at 80% -40px, rgba(76, 154, 71, .06), transparent 60%),
    var(--c-bg);
}

.hero-ink { position: absolute; left: 0; right: 0; bottom: -2px; width: 100%; height: 150px; pointer-events: none; }

.hero-inner { display: flex; align-items: flex-end; justify-content: space-between; gap: 24px; position: relative; }

.hero-eyebrow {
  margin: 0 0 10px; font-size: 13px; color: var(--c-muted); letter-spacing: 6px;
  display: inline-flex; align-items: center; gap: 10px;
}
.hero-eyebrow::before { content: ''; width: 26px; height: 1px; background: var(--c-accent); }

.hero-title {
  font-size: clamp(30px, 5vw, 42px); letter-spacing: 10px;
  color: var(--c-text); text-indent: 10px;
}

.hero-date { margin: 12px 0 14px; color: var(--c-muted); font-size: 15px; letter-spacing: 2px; }

.hero-motto {
  display: inline-block; margin: 0;
  font-family: var(--font-serif); font-size: 16px; letter-spacing: 3px;
  color: var(--c-primary); border-left: 3px solid var(--c-primary); padding-left: 14px;
}

.hero-side {
  writing-mode: vertical-rl; letter-spacing: 8px; font-size: 13px;
  color: var(--c-muted); opacity: .75; white-space: nowrap;
  border-left: 1px solid var(--c-line); padding-left: 10px;
}

/* ============ 页面主体 ============ */
.page { padding: 30px 20px 76px; }
.card {
  background: var(--c-card); border: 1px solid var(--c-line);
  border-radius: var(--r); box-shadow: var(--shadow-card);
  animation: rise .5s ease both;
}
.card + .card { margin-top: 22px; }

@keyframes rise {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: none; }
}

/* ============ 题目卡 ============ */
.question-card { padding: 30px 32px 26px; position: relative; }
.question-card::before {
  content: ''; position: absolute; top: 0; left: 32px; right: 32px; height: 2px;
  background: linear-gradient(90deg, var(--c-primary), transparent 70%);
  border-radius: var(--r);
}

.q-head { display: flex; align-items: center; gap: 14px; flex-wrap: wrap; }

.q-seal {
  width: 46px; height: 46px; flex: 0 0 auto;
  display: grid; place-items: center;
  border: 2px solid var(--c-accent); color: var(--c-accent);
  font-family: var(--font-serif); font-weight: 700; font-size: 22px;
  border-radius: var(--r); background: var(--c-accent-soft);
  transform: rotate(-3deg);
}

.q-meta { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }

.tag {
  display: inline-flex; align-items: center; gap: 4px;
  padding: 1px 10px; border: 1px solid var(--c-line); border-radius: var(--r);
  font-size: 12.5px; color: var(--c-muted); background: #fff; white-space: nowrap;
}
.tag-grade { color: var(--c-primary); border-color: var(--c-primary); background: var(--c-primary-soft); }
.tag-topic { color: var(--c-accent); border-color: var(--c-accent); background: var(--c-accent-soft); }
.tag-diff  { font-family: var(--font-serif); letter-spacing: 1px; }
.tag-date  { font-family: var(--font-serif); font-variant-numeric: tabular-nums; }

.stars { color: var(--c-accent); letter-spacing: 2px; font-size: 13px; }

.q-title { font-size: 24px; letter-spacing: 2px; margin: 22px 0 12px; }
.q-text {
  font-size: 17px; line-height: 2.1; margin: 0 0 8px;
  text-align: justify; padding-bottom: 4px;
}
.q-text::first-letter {
  font-family: var(--font-serif); font-size: 46px; line-height: 1;
  float: left; padding: 8px 10px 0 0; color: var(--c-primary); font-weight: 700;
}

.q-actions { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 18px; }

/* ============ 按钮 ============ */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 9px 22px; border-radius: var(--r); border: 1px solid transparent;
  font-family: var(--font-serif); font-size: 15px; letter-spacing: 1px;
  cursor: pointer; user-select: none;
  transition: transform .15s ease, box-shadow .2s ease, background .2s ease, color .2s, border-color .2s, filter .2s;
}
.btn:active { transform: translateY(1px) scale(.99); }

.btn-ghost { background: #fff; border-color: var(--c-line); color: var(--c-text); }
.btn-ghost:hover { border-color: var(--c-primary); color: var(--c-primary); box-shadow: var(--shadow-card); }
.btn-ghost.active { background: var(--c-primary-soft); border-color: var(--c-primary); color: var(--c-primary); font-weight: 700; }

.btn-cta { background: var(--c-cta); color: #fff; box-shadow: 0 4px 14px rgba(68, 187, 96, .28); }
.btn-cta:hover { filter: brightness(.96); box-shadow: 0 6px 18px rgba(68, 187, 96, .34); }

.btn-arrow { transition: transform .2s ease; }
.btn:hover .btn-arrow { transform: translateX(3px); }

/* ============ 折叠面板 ============ */
.panel { max-height: 0; overflow: hidden; transition: max-height .5s cubic-bezier(.22, 1, .36, 1); }

.panel-inner {
  padding: 0 6px 0 0; margin-top: 0;
  opacity: 0; transform: translateY(-4px);
  transition: opacity .35s .12s, transform .35s .12s;
}
.panel.open { max-height: 2400px; }
.panel.open .panel-inner {
  opacity: 1; transform: none;
  margin-top: 22px; padding-top: 18px; padding-bottom: 4px;
  border-top: 1px dashed var(--c-line);
}

.panel-title {
  display: flex; align-items: center; gap: 10px;
  font-size: 17px; letter-spacing: 2px; margin: 0 0 10px;
}
.panel-ic {
  width: 24px; height: 24px; flex: 0 0 auto; display: grid; place-items: center;
  background: var(--c-accent-soft); color: var(--c-accent);
  border: 1px solid var(--c-accent); border-radius: var(--r);
  font-family: var(--font-serif); font-size: 13px;
}

.sol-text { margin: 0 0 14px; text-align: justify; }

.steps { list-style: none; margin: 4px 0 0; padding: 0; display: grid; gap: 10px; }
.steps li { display: flex; gap: 12px; align-items: flex-start; }
.step-no {
  flex: 0 0 auto; min-width: 88px; padding: 2px 10px; text-align: center;
  border: 1px solid var(--c-primary); color: var(--c-primary);
  background: var(--c-primary-soft); border-radius: var(--r);
  font-family: var(--font-serif); font-size: 13.5px;
}
.step-c { flex: 1; min-width: 0; }

/* ============ 图文解析 / 视频 ============ */
.figure-box {
  margin: 14px 0 6px; padding: 14px 18px;
  border: 1px solid var(--c-line); border-left: 3px solid var(--c-primary);
  border-radius: var(--r); background: linear-gradient(180deg, var(--c-primary-soft), transparent 55%), #fff;
}
.figure-label {
  display: inline-block; margin-bottom: 8px; padding: 1px 10px;
  background: var(--c-primary); color: #fff; border-radius: var(--r);
  font-family: var(--font-serif); font-size: 12.5px; letter-spacing: 2px;
}
.figure-text {
  margin: 0; font-family: var(--font-serif); font-size: 14.5px; line-height: 2;
  white-space: pre-line; color: var(--c-text);
}

.video-note {
  display: flex; gap: 14px; align-items: flex-start;
  margin: 14px 0 4px; padding: 12px 16px;
  border: 1px solid var(--c-line); border-radius: var(--r); background: #fff;
}
.video-ic {
  flex: 0 0 auto; width: 34px; height: 34px; display: grid; place-items: center;
  background: var(--c-accent); color: #fff; border-radius: var(--r); font-size: 13px;
}
.video-note strong { font-family: var(--font-serif); letter-spacing: 1px; }
.video-note p { margin: 2px 0 0; font-size: 13.5px; color: var(--c-muted); }

/* ============ 小试身手 ============ */
.answer-box {
  margin-top: 18px; padding: 16px 18px;
  border: 1px dashed var(--c-line); border-radius: var(--r); background: var(--c-bg);
}
.answer-row { display: flex; gap: 10px; flex-wrap: wrap; }
.answer-input {
  flex: 1 1 180px; min-width: 0; padding: 9px 14px;
  border: 1px solid var(--c-line); border-radius: var(--r);
  font-size: 16px; color: var(--c-text); background: #fff;
}
.answer-input:focus { outline: none; border-color: var(--c-primary); box-shadow: 0 0 0 3px var(--c-primary-soft); }
.answer-result { margin: 10px 0 0; font-size: 14.5px; }
.answer-result.ok  { color: var(--c-primary); }
.answer-result.bad { color: var(--c-accent); }

/* ============ 昨日 / 明日导航 ============ */
.day-nav {
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  margin-top: 22px; padding: 14px 6px;
}
.day-btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 9px 18px; border: 1px solid var(--c-line); border-radius: var(--r);
  background: var(--c-card); color: var(--c-text); font-family: var(--font-serif); font-size: 15px;
  transition: color .2s, border-color .2s, box-shadow .2s, transform .15s;
}
.day-btn:hover { color: var(--c-primary); border-color: var(--c-primary); box-shadow: var(--shadow-card); }
.day-btn:active { transform: translateY(1px); }
.day-arrow { color: var(--c-primary); }
.day-caption {
  display: inline-flex; align-items: center; gap: 12px;
  color: var(--c-muted); font-size: 13.5px; letter-spacing: 1px; text-align: center;
}
.day-caption i { width: 1px; height: 14px; background: var(--c-line); }
.day-caption b { color: var(--c-text); font-weight: 600; font-family: var(--font-serif); }

.cta-band {
  margin-top: 26px; padding: 26px 30px; text-align: center;
  border: 1px solid var(--c-line); border-radius: var(--r);
  background: linear-gradient(180deg, var(--c-primary-soft), rgba(255,255,255,0) 80%), var(--c-card);
}
.cta-text { font-family: var(--font-serif); letter-spacing: 2px; color: var(--c-muted); margin: 0 0 14px; }

/* ============ 面包屑 / 分页 ============ */
.breadcrumb { padding: 18px 20px 0; font-size: 13.5px; color: var(--c-muted); letter-spacing: 1px; }
.breadcrumb a:hover { text-decoration: underline; }
.breadcrumb span { margin: 0 8px; color: var(--c-line); }

.pager { display: flex; justify-content: space-between; gap: 12px; margin-top: 26px; flex-wrap: wrap; }
.pager-link {
  flex: 1 1 220px; display: flex; flex-direction: column; gap: 2px;
  padding: 14px 18px; border: 1px solid var(--c-line); border-radius: var(--r);
  background: var(--c-card); color: var(--c-text);
  transition: color .2s, border-color .2s, box-shadow .2s, transform .15s;
}
.pager-link:hover { color: var(--c-primary); border-color: var(--c-primary); box-shadow: var(--shadow-card); }
.pager-link.is-next { text-align: right; align-items: flex-end; }
.pager-dir { font-size: 12px; color: var(--c-muted); letter-spacing: 2px; }
.pager-name { font-family: var(--font-serif); font-size: 15px; }

/* ============ 详细解析页 ============ */
.detail-card { padding: 30px 34px 28px; }

.detail-hero { display: flex; gap: 18px; align-items: flex-start; flex-wrap: wrap; }
.detail-seal {
  width: 54px; height: 54px; flex: 0 0 auto; display: grid; place-items: center;
  background: var(--c-primary); color: #fff; border-radius: var(--r);
  font-family: var(--font-serif); font-size: 24px; font-weight: 700;
  transform: rotate(-3deg); box-shadow: 0 4px 12px rgba(76, 154, 71, .3);
}
.detail-title { font-size: 26px; letter-spacing: 3px; }
.detail-meta .q-meta { margin-top: 8px; }

.detail-section { margin-top: 26px; }
.section-title {
  display: flex; align-items: center; gap: 12px;
  font-size: 19px; letter-spacing: 3px; margin-bottom: 14px;
}
.sec-no {
  flex: 0 0 auto; min-width: 34px; height: 28px; display: grid; place-items: center;
  padding: 0 6px; background: var(--c-primary); color: #fff; border-radius: var(--r);
  font-family: var(--font-serif); font-size: 15px; letter-spacing: 1px;
}
.hint-box {
  padding: 14px 18px; border: 1px solid var(--c-line); border-left: 3px solid var(--c-accent);
  border-radius: var(--r); background: var(--c-accent-soft); color: var(--c-text); text-align: justify;
}

.q-count { font-family: var(--font-sans); font-size: 13px; color: var(--c-muted); letter-spacing: 1px; font-weight: 400; margin-left: 8px; }
.q-count b { color: var(--c-primary); font-size: 15px; }

/* ============ 专题题库页 ============ */
.toolbar { padding: 22px 26px; }
.search-box {
  display: flex; align-items: center; gap: 10px;
  border: 1px solid var(--c-line); border-radius: var(--r); background: #fff;
  padding: 0 14px; transition: border-color .2s, box-shadow .2s;
}
.search-box:focus-within { border-color: var(--c-primary); box-shadow: 0 0 0 3px var(--c-primary-soft); }
.search-ic {
  flex: 0 0 auto; width: 22px; height: 22px; display: grid; place-items: center;
  border: 1px solid var(--c-primary); color: var(--c-primary); border-radius: var(--r);
  font-family: var(--font-serif); font-size: 11px;
}
.search-box input {
  flex: 1; min-width: 0; border: none; outline: none; background: transparent;
  padding: 12px 0; font-size: 15px; color: var(--c-text); font-family: var(--font-sans);
}
.search-box input::placeholder { color: #9db79b; }

.chip-group { display: flex; align-items: flex-start; gap: 12px; margin-top: 16px; flex-wrap: wrap; }
.chip-label {
  flex: 0 0 auto; padding-top: 5px; font-size: 12.5px; color: var(--c-muted);
  letter-spacing: 3px; font-family: var(--font-serif);
}
.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  padding: 4px 13px; border: 1px solid var(--c-line); border-radius: var(--r);
  background: #fff; color: var(--c-muted); font-size: 13.5px; cursor: pointer;
  transition: color .2s, background .2s, border-color .2s, transform .15s;
}
.chip:hover { color: var(--c-primary); border-color: var(--c-primary); }
.chip:active { transform: translateY(1px); }
.chip.active { background: var(--c-primary); border-color: var(--c-primary); color: #fff; font-weight: 600; }

.topic-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 14px; margin-top: 6px; }
.topic-card {
  display: flex; flex-direction: column; gap: 4px; text-align: left;
  padding: 18px 20px; border: 1px solid var(--c-line); border-radius: var(--r);
  background: var(--c-card); cursor: pointer; font-family: var(--font-sans);
  transition: transform .18s ease, box-shadow .2s ease, border-color .2s;
}
.topic-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-lift); border-color: var(--c-primary); }
.topic-name { font-family: var(--font-serif); font-size: 17px; letter-spacing: 2px; color: var(--c-text); }
.topic-count { font-size: 12.5px; color: var(--c-primary); font-family: var(--font-serif); }
.topic-grades { font-size: 12px; color: var(--c-muted); }

.q-list { display: grid; gap: 12px; margin-top: 6px; }
.q-item {
  display: flex; align-items: center; gap: 16px;
  padding: 16px 20px; border: 1px solid var(--c-line); border-radius: var(--r);
  background: var(--c-card); color: var(--c-text);
  transition: transform .18s ease, box-shadow .2s ease, border-color .2s;
}
.q-item:hover { transform: translateY(-2px); box-shadow: var(--shadow-lift); border-color: var(--c-primary); }
.q-item-seal {
  flex: 0 0 auto; width: 40px; height: 40px; display: grid; place-items: center;
  border: 1px solid var(--c-accent); color: var(--c-accent); background: var(--c-accent-soft);
  border-radius: var(--r); font-family: var(--font-serif); font-size: 16px;
}
.q-item-main { flex: 1; min-width: 0; display: flex; flex-direction: column; gap: 2px; }
.q-item-top { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.q-item-title { font-family: var(--font-serif); font-size: 16.5px; letter-spacing: 1px; }
.q-item-text {
  margin: 0; font-size: 14px; color: var(--c-muted);
  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
.q-item-tags { display: flex; gap: 6px; margin-top: 4px; flex-wrap: wrap; }
.q-item-arrow { color: var(--c-primary); opacity: 0; transform: translateX(-6px); transition: opacity .2s, transform .2s; }
.q-item:hover .q-item-arrow { opacity: 1; transform: none; }

.empty-note {
  padding: 30px; text-align: center; color: var(--c-muted);
  border: 1px dashed var(--c-line); border-radius: var(--r); font-family: var(--font-serif); letter-spacing: 1px;
}

/* ============ 页脚 ============ */
.site-footer {
  border-top: 1px solid var(--c-line); padding: 36px 0 46px; text-align: center;
}
.footer-motto {
  font-family: var(--font-serif); letter-spacing: 8px; color: var(--c-primary);
  margin: 0 0 8px; text-indent: 8px;
}
.footer-note { font-size: 12.5px; color: var(--c-muted); margin: 0; letter-spacing: 1px; }

/* ============ 响应式 ============ */
@media (max-width: 720px) {
  .header-inner { flex-direction: column; padding: 12px 0; gap: 8px; }
  .question-card, .toolbar, .detail-card { padding: 22px 18px; }
  .question-card::before { left: 18px; right: 18px; }
  .hero { padding: 40px 0 36px; }
  .hero-inner { flex-direction: column; align-items: flex-start; }
  .hero-side { display: none; }
  .day-nav { flex-direction: column; }
  .day-caption i { display: none; }
  .steps li { flex-direction: column; gap: 2px; }
  .step-no { min-width: 0; text-align: left; }
  .pager { flex-direction: column; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .01ms !important; transition-duration: .01ms !important; }
}