:root {
  --primary: #2563eb;
  --primary-700: #1d4ed8;
  --primary-50: #eff6ff;
  --bg: #f4f6f9;
  --card: #ffffff;
  --border: #e6e8ee;
  --text: #1f2937;
  --muted: #6b7280;
  --faint: #9aa1ac;
  --danger: #dc2626;
  --success: #16a34a;
  --warning: #d97706;
  --radius: 12px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  font-size: 15px;
  line-height: 1.6;
  -webkit-text-size-adjust: 100%;
}

.hidden { display: none !important; }

a { color: var(--primary); text-decoration: none; }

/* ---------- 认证页 ---------- */
.auth-wrap {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
}
.auth-card {
  width: 100%;
  max-width: 380px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 28px 24px;
}
.auth-card h1 { font-size: 20px; margin: 0 0 4px; font-weight: 600; }
.auth-card .sub { color: var(--muted); font-size: 13px; margin: 0 0 20px; }

/* ---------- 顶部栏与导航 ---------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  background: var(--card);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
}
.topbar .brand { font-weight: 600; font-size: 16px; }
.topbar .brand span { color: var(--primary); }
.topbar-right { display: flex; align-items: center; gap: 10px; font-size: 13px; color: var(--muted); }

.class-switcher { flex: 1; display: flex; justify-content: center; margin: 0 12px; min-width: 0; }
.class-switch-inner { display: flex; align-items: center; gap: 8px; max-width: 100%; }
.class-switch-inner select {
  max-width: 180px; font-size: 13px; padding: 5px 8px; border: 1px solid var(--border);
  border-radius: 8px; background: var(--card); color: var(--text);
}
.class-role { font-size: 12px; color: var(--muted); white-space: nowrap; }
.class-manage-link { color: var(--muted); text-decoration: none; font-size: 15px; }
.class-manage-link:hover { color: var(--primary); }
@media (max-width: 719px) {
  .class-switcher { margin: 0 6px; }
  .class-switch-inner select { max-width: 110px; }
  .class-role { display: none; }
}

.tabnav {
  position: sticky;
  top: 49px;
  z-index: 19;
  background: var(--card);
  border-bottom: 1px solid var(--border);
  display: flex;
  gap: 4px;
  padding: 0 16px;
}
.tabnav a {
  padding: 10px 14px;
  color: var(--muted);
  font-size: 14px;
  border-bottom: 2px solid transparent;
}
.tabnav a.active { color: var(--primary); border-bottom-color: var(--primary); font-weight: 600; }

.bottomnav {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  z-index: 19;
  background: var(--card);
  border-top: 1px solid var(--border);
  display: none;
  grid-template-columns: repeat(4, 1fr);
}
.bottomnav a {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  padding: 8px 0 10px;
  font-size: 11px;
  color: var(--muted);
}
.bottomnav a.active { color: var(--primary); font-weight: 600; }
.bottomnav svg { width: 22px; height: 22px; }

main { max-width: 1100px; margin: 0 auto; padding: 16px; padding-bottom: 84px; }

/* ---------- 通用组件 ---------- */
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  margin-bottom: 16px;
}
.card h2 { font-size: 15px; margin: 0 0 12px; font-weight: 600; }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--text);
  border-radius: 8px;
  padding: 8px 14px;
  font-size: 14px;
  cursor: pointer;
  transition: background .12s;
}
.btn:hover { background: #f0f2f6; }
.btn.primary { background: var(--primary); border-color: var(--primary); color: #fff; }
.btn.primary:hover { background: var(--primary-700); }
.btn.danger { color: var(--danger); border-color: #fecaca; }
.btn.small { padding: 4px 10px; font-size: 13px; }
.btn.block { width: 100%; }

input, select, textarea {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 9px 12px;
  font-size: 14px;
  font-family: inherit;
  background: var(--card);
  color: var(--text);
}
input:focus, select:focus, textarea:focus { outline: none; border-color: var(--primary); }
label { font-size: 13px; color: var(--muted); display: block; margin-bottom: 4px; }
.field { margin-bottom: 12px; }

.searchbar {
  display: flex;
  gap: 8px;
  margin-bottom: 14px;
}
.searchbar input { flex: 1; }

.empty { text-align: center; color: var(--muted); padding: 40px 16px; font-size: 14px; }

/* 学生卡片列表 */
.student-list { display: grid; grid-template-columns: 1fr; gap: 10px; }
.student-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 16px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 12px;
  transition: border-color .12s;
}
.student-card:hover { border-color: var(--primary); }
.avatar {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--primary-50);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
  flex-shrink: 0;
}
.student-card .info { flex: 1; min-width: 0; }
.student-card .name { font-weight: 600; }
.student-card .meta { font-size: 12px; color: var(--muted); }

.tag {
  display: inline-block;
  font-size: 11px;
  background: var(--primary-50);
  color: var(--primary);
  border-radius: 20px;
  padding: 1px 9px;
  margin-right: 4px;
}
.tag.warn { background: #fef3c7; color: #b45309; }

/* 指标卡 */
.metrics { display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px; margin-bottom: 16px; }
.metric { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); padding: 14px; }
.metric .label { font-size: 12px; color: var(--muted); }
.metric .value { font-size: 22px; font-weight: 600; margin-top: 2px; }
.metric .value.good { color: var(--success); }
.metric .value.bad { color: var(--danger); }

/* 分段切换 */
.seg { display: inline-flex; background: var(--bg); border: 1px solid var(--border); border-radius: 8px; padding: 3px; gap: 3px; }
.seg button {
  border: none;
  background: transparent;
  padding: 5px 12px;
  font-size: 13px;
  border-radius: 6px;
  cursor: pointer;
  color: var(--muted);
}
.seg button.active { background: var(--card); color: var(--primary); font-weight: 600; box-shadow: 0 0 0 1px var(--border); }

/* 表格 */
.table-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; font-size: 13px; }
th, td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--border); }
th { color: var(--muted); font-weight: 500; white-space: nowrap; }
td.num { font-variant-numeric: tabular-nums; }

/* 弹窗 */
.modal-mask {
  position: fixed;
  inset: 0;
  z-index: 50;
  background: rgba(0,0,0,.4);
  display: flex;
  align-items: flex-end;
  justify-content: center;
}
.modal {
  background: var(--card);
  width: 100%;
  max-width: 560px;
  max-height: 90vh;
  overflow-y: auto;
  border-radius: 16px 16px 0 0;
  padding: 20px;
}
.modal h3 { margin: 0 0 16px; font-size: 16px; }
.modal-foot { display: flex; gap: 10px; justify-content: flex-end; margin-top: 16px; }
.row { display: flex; gap: 10px; }
.row > * { flex: 1; }

.toast {
  position: fixed;
  left: 50%;
  bottom: 90px;
  transform: translateX(-50%);
  background: #111827;
  color: #fff;
  padding: 10px 18px;
  border-radius: 8px;
  font-size: 14px;
  z-index: 99;
  max-width: 90%;
  opacity: 0;
  pointer-events: none;
  transition: opacity .2s;
}
.toast.show { opacity: 1; }

/* 导入向导 */
.wizard-step { margin-bottom: 16px; }
.dropzone {
  border: 2px dashed var(--border);
  border-radius: var(--radius);
  padding: 32px 16px;
  text-align: center;
  color: var(--muted);
  cursor: pointer;
  background: #fafbfc;
}
.dropzone.drag { border-color: var(--primary); background: var(--primary-50); }
.map-row { display: flex; align-items: center; gap: 10px; padding: 6px 0; border-bottom: 1px solid var(--border); font-size: 13px; }
.map-row select { width: auto; min-width: 140px; }
.sample-table { max-height: 300px; overflow: auto; }
.sample-table th, .sample-table td { white-space: nowrap; }

.chart-box { position: relative; height: 280px; }

@media (min-width: 720px) {
  .student-list { grid-template-columns: repeat(2, 1fr); }
  .metrics { grid-template-columns: repeat(4, 1fr); }
  .modal { align-items: center; border-radius: 16px; margin: 24px; }
  .modal-mask { align-items: center; }
  .bottomnav { display: none; }
  .tabnav { display: flex; }
}
@media (max-width: 719px) {
  .tabnav { display: none; }
  .bottomnav { display: grid; }
}