/* ==========================================================================
   Merit Study Resources — Teacher library (curriculum / lesson browser)
   Loaded after style.css, resources.css and pages.css; reuses their tokens.
   1. Header  2. Filter bar  3. Layout  4. Topic sidebar  5. Course head
   6. Tool buttons  7. Lesson list  8. Empty state  9. Responsive
   ========================================================================== */

.page-teacher {
  --page-bg: #f6f8f7;
  --card-border: #e3e9e5;
  background: var(--page-bg);
}

/* 1. Header ------------------------------------------------------------- */
.tl-header {
  position: sticky;
  top: 0;
  z-index: 1030;
  background: #fff;
  border-bottom: 1px solid var(--merit-line);
}
.tl-header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 68px;
}
.tl-header .brand-mark { width: 40px; height: 40px; }
.tl-header .brand-name { font-size: .98rem; letter-spacing: .01em; }
.tl-header .brand-tagline { margin-top: .2rem; font-size: .52rem; letter-spacing: .16em; }

.tl-header-nav { display: flex; align-items: center; gap: .5rem; }
.tl-nav-link {
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  padding: .45rem .75rem;
  border-radius: var(--radius-sm);
  font-size: .88rem;
  font-weight: 600;
  color: var(--merit-text);
}
.tl-nav-link:hover { color: var(--merit-dark-green); background: var(--merit-light-green); text-decoration: none; }
.tl-nav-link.is-active { color: var(--merit-green); }

.member-pill {
  display: inline-flex;
  align-items: center;
  gap: .45rem;
  padding: .35rem .8rem .35rem .4rem;
  border: 1px solid var(--merit-border);
  border-radius: var(--radius-pill);
  background: #fff;
  font-size: .8rem;
  font-weight: 600;
  color: var(--merit-navy);
  transition: border-color var(--ease), background var(--ease);
}
.member-pill:hover { border-color: #cfe5d8; background: var(--merit-light-green); color: var(--merit-navy); text-decoration: none; }
.member-avatar {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: var(--merit-green);
  color: #fff;
  font-size: .68rem;
  font-weight: 700;
}

/* 2. Filter bar --------------------------------------------------------- */
.tl-filters {
  background: #fff;
  border-bottom: 1px solid var(--card-border);
  padding: 1rem 0 1.1rem;
}
.tl-filter-row {
  display: grid;
  grid-template-columns: 150px 150px 150px minmax(0, 1fr);
  gap: .75rem 1rem;
  align-items: end;
}
.tl-field-label {
  display: block;
  margin-bottom: .35rem;
  font-size: .74rem;
  font-weight: 600;
  color: var(--merit-muted);
}
.tl-select {
  min-height: 44px;
  border: 1px solid var(--merit-border);
  border-radius: var(--radius-sm);
  font-size: .9rem;
  font-weight: 500;
  color: var(--merit-navy);
  transition: border-color var(--ease), box-shadow var(--ease);
}
.tl-select:focus { border-color: var(--merit-green); box-shadow: 0 0 0 3px rgba(22, 138, 69, .1); }
.tl-filters .search-shell { min-height: 44px; padding-right: .5rem; }
.search-kbd {
  flex: none;
  padding: .1rem .45rem;
  border: 1px solid var(--merit-border);
  border-radius: 5px;
  background: #f6f8f7;
  font-size: .7rem;
  font-weight: 600;
  color: var(--merit-muted);
}

/* 3. Layout -------------------------------------------------------------- */
.tl-body { padding: 0 0 3rem; }
.tl-layout {
  display: grid;
  grid-template-columns: 270px minmax(0, 1fr);
  min-height: calc(100vh - 160px);
}

/* 4. Topic sidebar ------------------------------------------------------ */
.tl-sidebar {
  position: sticky;
  top: 68px;
  align-self: start;
  max-height: calc(100vh - 68px);
  overflow-y: auto;
  padding: 1.5rem 1.25rem 1.5rem 0;
  border-right: 1px solid var(--card-border);
}
.tl-side-title {
  display: flex;
  align-items: center;
  gap: .45rem;
  margin: 0;
  font-size: .95rem;
  font-weight: 700;
  color: var(--merit-navy);
}
.tl-side-title i { font-size: .75rem; color: var(--merit-green); }
.tl-side-sub {
  margin: .25rem 0 1rem 1.2rem;
  font-size: .66rem;
  font-weight: 700;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--merit-muted);
}

.topic-nav { display: grid; gap: .15rem; margin: 0; }
.topic-link {
  position: relative;
  display: flex;
  align-items: center;
  gap: .75rem;
  width: 100%;
  padding: .7rem .8rem;
  border: 0;
  border-radius: var(--radius-sm);
  background: transparent;
  text-align: left;
  font-size: .88rem;
  font-weight: 500;
  line-height: 1.35;
  color: var(--merit-text);
  transition: background var(--ease), color var(--ease);
}
.topic-link:hover { background: #fff; color: var(--merit-dark-green); }
.topic-link.is-active {
  background: #fff;
  color: var(--merit-dark-green);
  font-weight: 700;
  box-shadow: var(--shadow-xs), inset 3px 0 0 var(--merit-green);
}
.topic-num {
  flex: none;
  width: 22px;
  font-size: .72rem;
  font-weight: 700;
  color: #a5b4ad;
  font-variant-numeric: tabular-nums;
}
.topic-link.is-active .topic-num { color: var(--merit-green); }
.topic-name { flex: 1 1 auto; min-width: 0; }
.topic-count {
  flex: none;
  min-width: 24px;
  padding: .05rem .4rem;
  border-radius: var(--radius-pill);
  background: #eef2f0;
  font-size: .7rem;
  font-weight: 700;
  text-align: center;
  color: var(--merit-muted);
}
.topic-link.is-active .topic-count { background: var(--merit-light-green); color: var(--merit-dark-green); }

.side-help {
  margin-top: 1.5rem;
  padding: 1rem;
  border: 1px solid #d9e9df;
  border-radius: var(--radius);
  background: var(--merit-light-green);
}
.side-help-title { margin: 0 0 .25rem; font-size: .86rem; font-weight: 700; color: var(--merit-navy); }
.side-help p { margin: 0 0 .65rem; font-size: .78rem; line-height: 1.5; color: #4a5f70; }
.side-help a { font-size: .8rem; font-weight: 600; }

/* 5. Course head -------------------------------------------------------- */
.tl-main { padding: 1.5rem 0 0 2rem; min-width: 0; }
.tl-main .course-crumbs { margin-bottom: 1.25rem; font-size: .8rem; }

.tl-eyebrow {
  display: flex;
  align-items: center;
  gap: .5rem;
  margin: 0 0 .5rem;
  font-size: .72rem;
  font-weight: 700;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: var(--merit-green);
}
.tl-eyebrow::before {
  content: "";
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--merit-green);
}
.tl-title {
  font-size: clamp(1.8rem, 1.2rem + 1.8vw, 2.4rem);
  font-weight: 800;
  letter-spacing: -.03em;
  margin: 0 0 .6rem;
}
.tl-lead { max-width: 40rem; margin: 0 0 .9rem; font-size: .98rem; line-height: 1.6; color: #4a5f70; }

.tl-stats { display: flex; flex-wrap: wrap; gap: .4rem; margin: 0 0 1.4rem; }
.tl-stat {
  display: inline-flex;
  align-items: center;
  gap: .35rem;
  padding: .28rem .7rem;
  border: 1px solid var(--card-border);
  border-radius: var(--radius-pill);
  background: #fff;
  font-size: .78rem;
  font-weight: 600;
  color: var(--merit-navy);
}
.tl-stat i { color: var(--merit-green); font-size: .8rem; }

/* 6. Tool buttons ------------------------------------------------------- */
.tl-tools { display: flex; flex-wrap: wrap; gap: .5rem; margin-bottom: 2.25rem; }
.tl-tool {
  display: inline-flex;
  align-items: center;
  gap: .5rem;
  min-height: 42px;
  padding: .5rem 1rem;
  border: 1px solid var(--merit-border);
  border-radius: var(--radius-sm);
  background: #fff;
  font-size: .86rem;
  font-weight: 600;
  color: var(--merit-navy);
  box-shadow: var(--shadow-xs);
  transition: border-color var(--ease), background var(--ease), color var(--ease);
}
.tl-tool i { font-size: .95rem; color: var(--merit-green); }
.tl-tool:hover { border-color: #cfe5d8; background: var(--merit-light-green); color: var(--merit-dark-green); text-decoration: none; }

/* 7. Lesson list -------------------------------------------------------- */
.unit-head {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: .85rem;
}
.unit-title { font-size: 1.3rem; font-weight: 800; letter-spacing: -.02em; margin: 0; }
.unit-meta { margin: .2rem 0 0; font-size: .82rem; color: var(--merit-muted); }
.unit-count {
  flex: none;
  font-size: .78rem;
  font-weight: 600;
  color: var(--merit-muted);
}

.lesson-list {
  margin: 0;
  padding: 0;
  list-style: none;
  background: #fff;
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}
.lesson-row {
  display: grid;
  grid-template-columns: 48px minmax(0, 1fr) auto;
  align-items: center;
  gap: 1rem;
  padding: 1.05rem 1.25rem;
  transition: background var(--ease);
}
.lesson-row + .lesson-row { border-top: 1px solid var(--merit-line); }
.lesson-row:hover { background: #fafcfb; }

.lesson-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  border-radius: 10px;
  background: var(--merit-light-green);
  font-size: .82rem;
  font-weight: 700;
  color: var(--merit-dark-green);
  font-variant-numeric: tabular-nums;
}
.lesson-title { margin: 0 0 .25rem; font-size: .98rem; font-weight: 700; letter-spacing: -.012em; }
.lesson-title a { color: var(--merit-navy); }
.lesson-title a:hover { color: var(--merit-dark-green); text-decoration: none; }

.lesson-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: .3rem .55rem;
  margin: 0;
  font-size: .78rem;
  color: var(--merit-muted);
}
.lesson-week { font-weight: 600; color: #4a5f70; }
.lesson-code {
  padding: .05rem .4rem;
  border-radius: 5px;
  background: #f1f4f3;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: .72rem;
  color: #4a5f70;
}
.lesson-dot { width: 3px; height: 3px; border-radius: 50%; background: #c3cfc8; }
.lesson-res { display: inline-flex; align-items: center; gap: .55rem; }
.lesson-res span { display: inline-flex; align-items: center; gap: .2rem; }
.lesson-res i { font-size: .78rem; color: #8aa096; }

.btn-open {
  display: inline-flex;
  align-items: center;
  gap: .5rem;
  min-height: 40px;
  padding: .45rem 1.05rem;
  font-size: .86rem;
  white-space: nowrap;
}
.btn-open i { transition: transform var(--ease); }
.lesson-row:hover .btn-open i { transform: translateX(3px); }

.unit-foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  margin-top: 1rem;
}
.unit-pager { display: flex; gap: .5rem; }
.unit-note { margin: 0; font-size: .8rem; color: var(--merit-muted); }

/* 8. Empty / search state ---------------------------------------------- */
.tl-empty {
  padding: 2.5rem 1rem;
  text-align: center;
  font-size: .92rem;
  color: var(--merit-muted);
}
.tl-empty i { display: block; margin-bottom: .5rem; font-size: 1.5rem; color: #b6c6bd; }
.lesson-topic-tag {
  display: inline-block;
  margin-bottom: .2rem;
  font-size: .68rem;
  font-weight: 700;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--merit-green);
}
mark { padding: 0 .1em; border-radius: 3px; background: #fdf1c7; color: inherit; }

/* 9. Responsive --------------------------------------------------------- */
@media (max-width: 1199.98px) {
  .tl-layout { grid-template-columns: 240px minmax(0, 1fr); }
  .tl-main { padding-left: 1.5rem; }
}

@media (max-width: 991.98px) {
  .tl-filter-row { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .tl-search { grid-column: 1 / -1; }

  .tl-layout { display: block; }
  /* sidebar becomes a horizontal, scrollable topic strip */
  .tl-sidebar {
    position: sticky;
    top: 68px;
    z-index: 1010;
    max-height: none;
    overflow: visible;
    margin: 0 calc(var(--bs-gutter-x, 1.5rem) * -.5);
    padding: .75rem calc(var(--bs-gutter-x, 1.5rem) * .5);
    border-right: 0;
    border-bottom: 1px solid var(--card-border);
    background: rgba(246, 248, 247, .96);
    backdrop-filter: saturate(140%) blur(6px);
  }
  .tl-side-title, .tl-side-sub, .side-help { display: none; }
  .topic-nav {
    display: flex;
    gap: .4rem;
    overflow-x: auto;
    scrollbar-width: none;
  }
  .topic-nav::-webkit-scrollbar { display: none; }
  .topic-link {
    flex: none;
    width: auto;
    padding: .45rem .85rem;
    border: 1px solid var(--merit-border);
    border-radius: var(--radius-pill);
    background: #fff;
    white-space: nowrap;
    font-size: .84rem;
  }
  .topic-link.is-active {
    border-color: var(--merit-green);
    background: var(--merit-green);
    color: #fff;
    box-shadow: none;
  }
  .topic-link.is-active .topic-count { background: rgba(255, 255, 255, .2); color: #fff; }
  .topic-num { display: none; }
  .tl-main { padding: 1.25rem 0 0; }
}

@media (max-width: 767.98px) {
  .tl-header-nav .tl-nav-link span { display: none; }
  .lesson-row {
    grid-template-columns: 40px minmax(0, 1fr);
    gap: .75rem;
    padding: 1rem;
  }
  .lesson-num { width: 34px; height: 34px; }
  .lesson-action { grid-column: 2; }
  .btn-open { min-height: 38px; }
  .unit-head { align-items: flex-start; flex-direction: column; gap: .2rem; }
}

@media (max-width: 575.98px) {
  .tl-filter-row { grid-template-columns: 1fr 1fr; }
  .tl-filter-row > :first-child { grid-column: 1 / -1; }
  .tl-tools { display: grid; grid-template-columns: 1fr; }
  .tl-tool { justify-content: center; }
  .member-pill .member-label { display: none; }
  .member-pill { padding-right: .4rem; }
  .search-kbd { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  .lesson-row:hover .btn-open i { transform: none; }
}

/* pager buttons at the first / last topic */
.unit-pager .btn-soft:disabled { opacity: .45; background: #fff; color: var(--merit-navy); border-color: var(--merit-border); }