/* ============================================================
   作业提交与管理系统 · 全局样式
   移动优先（学生多用手机扫码访问），桌面端两栏布局
   ============================================================ */

:root {
  --blue: #2563eb;
  --blue-dark: #1d4ed8;
  --blue-soft: #eff6ff;
  --green: #16a34a;
  --green-soft: #dcfce7;
  --amber: #d97706;
  --amber-soft: #fef3c7;
  --red: #dc2626;
  --red-soft: #fee2e2;
  --ink: #0f172a;
  --ink-2: #334155;
  --muted: #64748b;
  --line: #e2e8f0;
  --bg: #f1f5f9;
  --card: #ffffff;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(15, 23, 42, .06), 0 8px 24px -12px rgba(15, 23, 42, .12);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
}

body {
  font-family: "Microsoft YaHei", "PingFang SC", "Hiragino Sans GB", system-ui, -apple-system, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--ink);
  font-size: 15px;
  line-height: 1.6;
  -webkit-text-size-adjust: 100%;
}

a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; }
code {
  background: #f1f5f9;
  padding: 1px 5px;
  border-radius: 4px;
  font-family: Consolas, "Courier New", monospace;
  font-size: .9em;
}
h1, h2, h3, h4 { margin: 0 0 12px; line-height: 1.35; }
h1 { font-size: 1.5rem; }
h2 { font-size: 1.15rem; }
h3 { font-size: 1rem; }
p { margin: 0 0 10px; }
hr.divider { border: 0; border-top: 1px solid var(--line); margin: 18px 0; }

.muted { color: var(--muted); }
.small { font-size: .85rem; }
.req { color: var(--red); }
.ok-text { color: var(--green); }
.warn { color: var(--amber); }
.error-text { color: var(--red); }

/* ---------------- 顶栏 ---------------- */
.topbar {
  background: #fff;
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 20;
}
.topbar-inner {
  max-width: 1180px;
  margin: 0 auto;
  padding: 10px 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}
.brand { display: flex; align-items: center; gap: 9px; color: var(--ink); font-weight: 700; }
.brand:hover { text-decoration: none; }
.brand-mark {
  width: 30px; height: 30px;
  border-radius: 8px;
  background: var(--blue);
  color: #fff;
  display: grid; place-items: center;
  font-size: .8rem; letter-spacing: .5px;
}
.brand-text { font-size: .98rem; }
.nav { display: flex; align-items: center; gap: 14px; flex-wrap: wrap; }
.nav a { color: var(--ink-2); font-size: .92rem; }
.nav a:hover { color: var(--blue); text-decoration: none; }
.nav-cta {
  background: var(--blue);
  color: #fff !important;
  padding: 6px 14px;
  border-radius: 999px;
  font-size: .88rem;
}
.nav-cta:hover { background: var(--blue-dark); }

/* ---------------- 布局 ---------------- */
.container {
  max-width: 1180px;
  margin: 0 auto;
  padding: 20px 16px 48px;
}
.grid-2 {
  display: grid;
  grid-template-columns: 1fr;
  gap: 18px;
}
@media (min-width: 900px) {
  .grid-2 { grid-template-columns: 1.15fr .85fr; }
  .grid-2 > .card { margin-bottom: 0; }
}
.page-head {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 12px;
  flex-wrap: wrap;
  margin-bottom: 16px;
}
.page-head h1 { margin-bottom: 4px; }

/* ---------------- 卡片 ---------------- */
.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
  margin-bottom: 18px;
}
.card > h2:first-child { margin-top: 0; }
.hero h1 { margin-bottom: 6px; }
.center-card { max-width: 520px; margin: 40px auto; text-align: center; }
.login-card { max-width: 400px; }
.error-code {
  font-size: 3.2rem;
  font-weight: 800;
  color: var(--blue);
  line-height: 1;
  margin-bottom: 8px;
}
.danger-zone { border-color: #fecaca; }

/* ---------------- 表单 ---------------- */
.form-item { margin-bottom: 15px; }
.form-item label {
  display: block;
  margin-bottom: 6px;
  font-size: .88rem;
  color: var(--ink-2);
  font-weight: 600;
}
input[type="text"], input[type="password"], input[type="datetime-local"],
input[type="file"], select, textarea {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid #cbd5e1;
  border-radius: 8px;
  font-size: .95rem;
  font-family: inherit;
  background: #fff;
  color: var(--ink);
}
input:focus, select:focus, textarea:focus {
  outline: none;
  border-color: var(--blue);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, .12);
}
input[type="file"] { padding: 8px; background: #f8fafc; }
select[multiple] { min-height: 120px; }
.form-row { display: grid; grid-template-columns: 1fr; gap: 0 14px; }
@media (min-width: 620px) { .form-row { grid-template-columns: 1fr 1fr; } }
.inline-form { display: flex; gap: 10px; flex-wrap: wrap; }
.inline-form input { flex: 1 1 200px; }
.hint { font-size: .82rem; color: var(--muted); margin: 6px 0 0; }
.checkbox-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 6px 14px;
  max-height: 220px;
  overflow: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px 12px;
  background: #f8fafc;
}
.checkbox { display: flex; align-items: center; gap: 8px; font-size: .9rem; font-weight: 400; cursor: pointer; }
.checkbox input { width: auto; }
.checkbox.inline { display: inline-flex; }

/* ---------------- 按钮 ---------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 10px 18px;
  border: 1px solid transparent;
  border-radius: 8px;
  font-size: .92rem;
  font-family: inherit;
  font-weight: 600;
  cursor: pointer;
  background: #e2e8f0;
  color: var(--ink);
  transition: background .15s, box-shadow .15s, opacity .15s;
}
.btn:hover { text-decoration: none; background: #cbd5e1; }
.btn-primary { background: var(--blue); color: #fff; }
.btn-primary:hover { background: var(--blue-dark); }
.btn-ghost { background: #fff; border-color: #cbd5e1; color: var(--ink-2); }
.btn-ghost:hover { background: #f8fafc; }
.btn-danger { background: var(--red); color: #fff; }
.btn-danger:hover { background: #b91c1c; }
.btn-small { padding: 5px 11px; font-size: .82rem; }
.btn-block { width: 100%; }
.btn:disabled { opacity: .6; cursor: not-allowed; }
.actions { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.actions-cell { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; }
form.inline { display: inline; }

/* ---------------- 提示 ---------------- */
.flashes { margin-bottom: 16px; }
.alert {
  padding: 12px 16px;
  border-radius: 8px;
  margin-bottom: 10px;
  font-size: .92rem;
  border: 1px solid transparent;
}
.alert-success { background: var(--green-soft); color: #14532d; border-color: #bbf7d0; }
.alert-error { background: var(--red-soft); color: #7f1d1d; border-color: #fecaca; }
.alert-warning { background: var(--amber-soft); color: #78350f; border-color: #fde68a; }
.alert-info { background: var(--blue-soft); color: #1e3a8a; border-color: #bfdbfe; }

/* ---------------- 徽章 ---------------- */
.badge {
  display: inline-block;
  padding: 2px 9px;
  border-radius: 999px;
  font-size: .78rem;
  font-weight: 600;
  white-space: nowrap;
}
.badge-ok { background: var(--green-soft); color: #14532d; }
.badge-warn { background: var(--amber-soft); color: #78350f; }
.badge-muted { background: #e2e8f0; color: var(--ink-2); }

/* ---------------- 表格 ---------------- */
.table-wrap { overflow-x: auto; -webkit-overflow-scrolling: touch; }
.data-table { width: 100%; border-collapse: collapse; font-size: .9rem; }
.data-table th, .data-table td {
  padding: 9px 12px;
  border-bottom: 1px solid var(--line);
  text-align: left;
  vertical-align: top;
}
.data-table th {
  background: #f8fafc;
  font-size: .82rem;
  color: var(--ink-2);
  font-weight: 700;
  white-space: nowrap;
}
.data-table tbody tr:hover { background: #f8fafc; }
.data-table.compact th, .data-table.compact td { padding: 6px 10px; font-size: .82rem; }
.file-cell { word-break: break-all; max-width: 240px; }

@media (max-width: 700px) {
  .data-table thead { display: none; }
  .data-table, .data-table tbody, .data-table tr, .data-table td { display: block; width: 100%; }
  .data-table tr {
    border: 1px solid var(--line);
    border-radius: 10px;
    margin-bottom: 10px;
    padding: 8px 10px;
    background: #fff;
  }
  .data-table td { border: 0; padding: 3px 0; display: flex; gap: 8px; }
  .data-table td::before {
    content: attr(data-label);
    flex: 0 0 74px;
    color: var(--muted);
    font-size: .8rem;
  }
}

/* ---------------- 统计 / 进度 ---------------- */
.stat-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 12px;
  margin-bottom: 18px;
}
.stat {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 14px;
  text-align: center;
  box-shadow: var(--shadow);
}
.stat-value { font-size: 1.4rem; font-weight: 800; color: var(--ink); }
.stat-value.ok { color: var(--green); }
.stat-value.warn { color: var(--amber); }
.stat-label { font-size: .8rem; color: var(--muted); margin-top: 2px; }

.progress {
  height: 7px;
  background: #e2e8f0;
  border-radius: 999px;
  overflow: hidden;
  margin-bottom: 4px;
  min-width: 90px;
}
.progress-bar { height: 100%; background: var(--blue); border-radius: 999px; }

/* ---------------- 列表 / 其它 ---------------- */
.task-list { list-style: none; padding: 0; margin: 0; }
.task-list li { padding: 9px 0; border-bottom: 1px dashed var(--line); }
.task-list li:last-child { border-bottom: 0; }
.task-line { display: flex; justify-content: space-between; gap: 10px; align-items: center; }
.task-meta { font-size: .82rem; color: var(--muted); }
.task-status { margin-top: 8px; }

.steps { padding-left: 20px; margin: 0; }
.steps li { margin-bottom: 7px; }
.faq { padding-left: 18px; margin: 0; font-size: .9rem; }
.faq li { margin-bottom: 6px; }
.empty { padding: 14px 0; }
.code-block {
  background: #0f172a;
  color: #e2e8f0;
  padding: 14px;
  border-radius: 10px;
  overflow-x: auto;
  font-size: .82rem;
  line-height: 1.6;
}

.history summary {
  cursor: pointer;
  font-size: .8rem;
  color: var(--blue);
  white-space: nowrap;
}
.history ul { list-style: none; padding: 6px 0 0 8px; margin: 0; }
.history li { display: flex; gap: 8px; align-items: center; padding: 2px 0; }
.student-list { display: flex; flex-wrap: wrap; gap: 6px; padding: 8px 0; max-width: 420px; }
.chip {
  background: #f1f5f9;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 2px 10px;
  font-size: .78rem;
}

/* ---------------- 上传遮罩 ---------------- */
.uploading {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 12px;
  padding: 10px 14px;
  background: var(--blue-soft);
  border: 1px solid #bfdbfe;
  border-radius: 8px;
  color: #1e3a8a;
  font-size: .9rem;
}
.uploading[hidden] { display: none; }
.spinner {
  width: 16px; height: 16px;
  border: 2px solid #93c5fd;
  border-top-color: var(--blue);
  border-radius: 50%;
  animation: spin .8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ---------------- 页脚 ---------------- */
.footer {
  max-width: 1180px;
  margin: 0 auto;
  padding: 18px 16px 32px;
  color: var(--muted);
  font-size: .82rem;
  text-align: center;
}
.footer-sep { margin: 0 6px; }