* { box-sizing: border-box; }
body { margin: 0; font-family: "Microsoft YaHei", Arial, sans-serif; color: #17212b; background: #f5f7f8; }
a { color: #106b6f; }
button { cursor: pointer; border: 0; border-radius: 6px; padding: 10px 14px; background: #176c72; color: white; font-size: 15px; }
button.secondary { background: #e8eff0; color: #173236; }
.login { min-height: 100vh; display: grid; grid-template-columns: 1.1fr .9fr; }
.login-info { padding: 70px 8vw; background: #12363b; color: #fff; }
.login-info h1 { font-size: 38px; margin: 0 0 18px; }
.login-info p { line-height: 1.9; color: #dce8e9; }
.login-panel { display: flex; align-items: center; justify-content: center; padding: 32px; }
.box { width: min(430px, 100%); background: #fff; border: 1px solid #dde5e7; border-radius: 8px; padding: 26px; }
.box h2 { margin: 0 0 18px; }
label { display: block; font-size: 14px; margin: 12px 0 6px; color: #4a5b61; }
input { width: 100%; padding: 11px 12px; border: 1px solid #cfd9dc; border-radius: 6px; font-size: 15px; }
.row { display: flex; gap: 10px; align-items: center; margin-top: 16px; }
.topbar { height: 62px; display: flex; align-items: center; justify-content: space-between; padding: 0 28px; background: #fff; border-bottom: 1px solid #dde5e7; position: sticky; top: 0; z-index: 4; }
.brand { font-weight: 700; }
.layout { max-width: 1220px; margin: 0 auto; padding: 28px; }
.hero { background: #fff; border: 1px solid #dde5e7; border-radius: 8px; padding: 28px; }
.hero h1 { margin: 0 0 14px; font-size: 30px; }
.hero p, .section p, .lesson p { line-height: 1.9; color: #3d4f55; }
.section { margin-top: 20px; background: #fff; border: 1px solid #dde5e7; border-radius: 8px; padding: 24px; }
.dept-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; margin-top: 16px; }
.dept-grid button { min-height: 54px; background: #f0f6f6; color: #143f43; border: 1px solid #cfe0e2; }
.dept-card { display: flex; flex-direction: column; gap: 7px; align-items: flex-start; justify-content: center; min-height: 112px; text-align: left; line-height: 1.45; }
.dept-card span { font-weight: 700; font-size: 16px; }
.dept-card small { color: #4f666b; font-size: 12px; line-height: 1.55; }
.video-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; margin-top: 16px; }
.video-card { display: flex; align-items: center; min-height: 72px; padding: 14px; border: 1px solid #cfe0e2; border-radius: 8px; background: #f0f6f6; color: #143f43; text-decoration: none; line-height: 1.5; }
.video-card:hover { background: #e5f0f1; }
.install-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px 16px; margin-top: 16px; max-width: 760px; }
.install-card { min-height: 128px; padding: 18px; border: 1px solid #d7e0df; border-radius: 8px; background: #fbfcfc; color: #173236; text-decoration: none; line-height: 1.55; }
.install-card strong { display: block; margin-bottom: 8px; color: #143f43; }
.install-card small { display: block; color: #52676c; font-size: 12px; }
.install-card:hover { background: #f0f6f6; }
button.install-card { width: 100%; text-align: left; cursor: pointer; }
.ai-tool-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 14px; margin: 14px 0 22px; }
.ai-tool-card { min-height: 132px; padding: 16px; border: 1px solid #dbe6e8; border-radius: 8px; background: #fbfcfc; }
.ai-tool-card strong { display: block; margin-bottom: 8px; color: #143f43; font-size: 17px; }
.ai-tool-card p { margin: 0; }
.codex-card { background: #edf4f5; border-color: #c7dcdf; }
.ai-compare-table td:first-child { width: 120px; }
.ai-compare-table td:nth-child(2) { width: 270px; }
.course-shell { display: grid; grid-template-columns: 190px 1fr; gap: 16px; align-items: start; }
.lesson { background: #fff; border: 1px solid #dde5e7; border-radius: 8px; padding: 24px; margin-bottom: 16px; }
.lesson h2 { margin-top: 0; }
.chapter-heading { display: flex; align-items: center; gap: 12px; padding-bottom: 14px; margin-bottom: 14px; border-bottom: 1px solid #e1e9eb; }
.chapter-heading span { flex: 0 0 auto; padding: 5px 9px; border-radius: 999px; background: #e7f1f2; color: #14565c; font-size: 13px; font-weight: 700; }
.chapter-heading h2 { margin: 0; color: #14292d; font-size: 22px; line-height: 1.25; }
.back-button { flex: 0 0 auto; width: 32px; height: 32px; padding: 0; border-radius: 7px; background: #e8eff0; color: #173236; font-size: 18px; line-height: 32px; }
.back-button:hover { background: #dce8ea; }
.course-links a { display: block; margin: 8px 0; }
.lesson-brief { margin: 14px 0 18px; border: 1px solid #dbe6e8; border-radius: 8px; background: #fbfcfc; }
.lesson-brief summary { padding: 12px 14px; cursor: pointer; color: #143f43; font-weight: 700; }
.lesson-brief p { margin: 0; padding: 0 14px 12px; }
.lesson-brief p:first-of-type { padding-top: 2px; }
.step-list { margin: 8px 0 18px; padding-left: 22px; color: #3d4f55; line-height: 1.9; }
.install-detail h3 { margin: 22px 0 8px; color: #173236; }
.nav { position: sticky; top: 82px; background: #fff; border: 1px solid #dde5e7; border-radius: 8px; padding: 10px; }
.nav a { display: block; padding: 9px 8px; text-decoration: none; border-radius: 6px; color: #1d484d; }
.nav a:hover { background: #edf4f5; }
.nav-link { display: block; width: 100%; margin-top: 7px; padding: 8px 7px; text-align: left; background: #fbfcfc; color: #1d484d; border: 1px solid #dbe6e8; border-radius: 7px; }
.nav-link:hover, .nav-link.active { background: #edf4f5; border-color: #cfe0e2; }
.chapter-link { display: grid; gap: 3px; padding: 9px 8px; }
.chapter-index { color: #176c72; font-size: 12px; font-weight: 700; }
.chapter-title { color: #1d3438; font-size: 13px; line-height: 1.4; }
.chapter-link.active .chapter-title { font-weight: 700; }
.scope-table-wrap { margin-top: 14px; overflow-x: auto; border: 1px solid #dbe6e8; border-radius: 8px; }
.scope-table { width: 100%; border-collapse: collapse; background: #fff; min-width: 820px; }
.scope-table th, .scope-table td { padding: 13px 14px; border-bottom: 1px solid #e6edef; text-align: left; vertical-align: top; line-height: 1.65; }
.scope-table th { background: #edf4f5; color: #143f43; font-weight: 700; }
.scope-table td:first-child { width: 160px; color: #173236; font-weight: 700; }
.scope-table td:nth-child(2) { width: 260px; color: #314a50; }
.scope-table tr:last-child td { border-bottom: 0; }
.checkin { margin-top: 18px; padding: 14px; background: #f3f7f7; border-radius: 8px; border: 1px solid #d8e4e6; }
.timer { font-weight: 700; color: #164f55; }
.muted { color: #6a7b80; font-size: 14px; }
.error { color: #a33; margin-top: 10px; }
@media (max-width: 860px) {
  .login { grid-template-columns: 1fr; }
  .login-info { padding: 36px 24px; }
  .dept-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .video-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .ai-tool-grid { grid-template-columns: 1fr; }
  .course-shell { grid-template-columns: 1fr; }
  .nav { position: static; }
  .install-grid { grid-template-columns: 1fr; max-width: none; }
  .chapter-heading { align-items: flex-start; flex-direction: column; gap: 10px; }
  .chapter-heading h2 { font-size: 20px; }
}