:root {
  --bg: #0f0f14;
  --surface: #16161f;
  --surface2: #1e1e2a;
  --border: #ffffff12;
  --text: #e2e2ec;
  --text-muted: #8888aa;
  --accent: #f7931a;
  --accent-dim: #f7931a22;
  --accent-border: #f7931a44;
  --radius: 12px;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.8;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Nav */
.nav {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
  position: sticky;
  top: 0;
  z-index: 100;
}
.nav-brand { font-weight: 800; font-size: 16px; color: var(--accent); }
.nav-links { display: flex; gap: 16px; align-items: center; }
.nav-links a, .nav-links button {
  color: var(--text-muted);
  font-size: 14px;
  background: none;
  border: none;
  cursor: pointer;
  font-family: inherit;
}
.nav-links a:hover, .nav-links button:hover { color: var(--text); text-decoration: none; }

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 18px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  border: none;
  font-family: inherit;
  transition: opacity .15s;
}
.btn:hover { opacity: .85; }
.btn-primary { background: var(--accent); color: #000; }
.btn-outline { background: transparent; border: 1px solid var(--border); color: var(--text); }
.btn-danger  { background: #e53e3e22; border: 1px solid #e53e3e44; color: #fc8181; }

/* Card */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
}

/* Form */
.form-group { margin-bottom: 16px; }
.form-group label { display: block; font-size: 13px; color: var(--text-muted); margin-bottom: 6px; }
.form-group input {
  width: 100%;
  padding: 10px 14px;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-size: 14px;
  font-family: inherit;
  outline: none;
  transition: border-color .15s;
}
.form-group input:focus { border-color: var(--accent); }

/* Login page */
.login-wrap {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
}
.login-box { width: 100%; max-width: 380px; }
.login-box h1 { font-size: 24px; margin-bottom: 8px; }
.login-box .sub { color: var(--text-muted); font-size: 14px; margin-bottom: 28px; }
.error-msg { color: #fc8181; font-size: 13px; margin-top: 8px; }

/* Container */
.container { max-width: 900px; margin: 0 auto; padding: 32px 24px; }

/* Search */
.search-wrap { margin-bottom: 24px; }
.search-wrap input {
  width: 100%;
  padding: 12px 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-size: 15px;
  font-family: inherit;
  outline: none;
}
.search-wrap input:focus { border-color: var(--accent); }

/* Course list */
.course-list { display: flex; flex-direction: column; gap: 2px; }
.course-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 18px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: border-color .15s, background .15s;
}
.course-item:hover { border-color: var(--accent-border); background: var(--surface2); }
.course-title { font-size: 15px; font-weight: 500; }
.course-date  { font-size: 12px; color: var(--text-muted); white-space: nowrap; margin-left: 12px; }
.course-count { font-size: 13px; color: var(--text-muted); margin-bottom: 16px; }

/* Lesson page */
.lesson-header {
  background: linear-gradient(160deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
  border-bottom: 1px solid var(--border);
  padding: 48px 24px 40px;
  text-align: center;
}
.lesson-header .badge {
  display: inline-flex;
  align-items: center;
  background: var(--accent-dim);
  border: 1px solid var(--accent-border);
  color: var(--accent);
  font-size: 12px;
  font-weight: 600;
  padding: 4px 12px;
  border-radius: 20px;
  margin-bottom: 16px;
}
.lesson-header h1 { font-size: clamp(20px, 4vw, 28px); font-weight: 800; color: #fff; max-width: 700px; margin: 0 auto 12px; }
.lesson-header .meta { color: var(--text-muted); font-size: 13px; }
.back-link { display: inline-flex; align-items: center; gap: 6px; color: var(--text-muted); font-size: 14px; margin-bottom: 24px; }
.back-link:hover { color: var(--text); text-decoration: none; }

/* Markdown body */
.md-body { max-width: 760px; margin: 0 auto; }
.md-body h1 { display: none; }
.md-body h2 { font-size: 18px; font-weight: 700; color: #fff; margin: 36px 0 12px; padding-bottom: 8px; border-bottom: 1px solid var(--border); }
.md-body h3 { font-size: 16px; font-weight: 600; margin: 24px 0 8px; }
.md-body p  { font-size: 15px; margin-bottom: 14px; line-height: 1.9; }
.md-body strong { color: #fff; }
.md-body em { color: var(--text-muted); font-style: normal; font-size: 13px; }
.md-body img { max-width: 100%; border-radius: var(--radius); border: 1px solid var(--border); display: block; margin: 16px auto; }
.md-body blockquote { border-left: 3px solid var(--accent); padding: 10px 18px; margin: 16px 0; background: var(--surface2); border-radius: 0 8px 8px 0; color: var(--text-muted); }
.md-body ul, .md-body ol { padding-left: 24px; margin-bottom: 14px; }
.md-body li { font-size: 15px; margin-bottom: 4px; }

/* Admin */
.admin-table { width: 100%; border-collapse: collapse; margin-top: 16px; }
.admin-table th { text-align: left; padding: 10px 14px; font-size: 12px; color: var(--text-muted); border-bottom: 1px solid var(--border); }
.admin-table td { padding: 12px 14px; border-bottom: 1px solid var(--border); font-size: 14px; }
.admin-table tr:last-child td { border-bottom: none; }

/* Pagination */
.pagination { display: flex; gap: 8px; justify-content: center; margin-top: 24px; flex-wrap: wrap; }
.pagination button {
  padding: 6px 12px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 13px;
  font-family: inherit;
}
.pagination button.active { background: var(--accent-dim); border-color: var(--accent-border); color: var(--accent); }
.pagination button:hover:not(.active) { border-color: var(--text-muted); }

@media (max-width: 600px) {
  .container { padding: 16px 12px; }

  /* Nav */
  .nav { padding: 0 16px; height: 50px; }
  .nav-brand { font-size: 14px; }
  .nav-links { gap: 10px; }
  .nav-links a, .nav-links button { font-size: 13px; }

  /* Course list */
  .course-item { padding: 12px 14px; flex-wrap: wrap; gap: 4px; }
  .course-title { font-size: 14px; width: 100%; }
  .course-date { margin-left: 0; font-size: 11px; }

  /* Lesson */
  .lesson-header { padding: 28px 16px 24px; }
  .lesson-header h1 { font-size: 18px; }
  .md-body h2 { font-size: 16px; }
  .md-body p, .md-body li { font-size: 14px; }

  /* Login */
  .login-box h1 { font-size: 20px; }

  /* Admin table */
  .admin-table th, .admin-table td { padding: 10px 8px; font-size: 13px; }
}