/* Chapters page styles (inherits tokens from main.css) */

/* --- Fluid, proportional type just for this page --- */
.chapters-page{
  /* caps for min/max keep things readable across widths */
  --fs-h1:   clamp(1.25rem, 1rem + 2vw, 2rem);
  --fs-sub:  clamp(.88rem,  .8rem + .7vw, 1rem);
  --fs-card: clamp(.95rem,  .9rem + .6vw, 1.05rem);
  --fs-btn:  clamp(.80rem,  .75rem + .6vw, .95rem);
  --fs-link: clamp(.90rem,  .85rem + .5vw, 1rem);
}

.chapters-page .page-head{
  padding: 1.25rem 0 .6rem;
  border-bottom: 1px solid var(--bs-border-color);
  text-align: center;
}
.chapters-page .subject-breadcrumb{
  margin-bottom: .5rem;
  font-size: .9rem;
  color: #64748b;
  display: flex;
  flex-wrap: wrap;
  gap: .35rem;
  justify-content: flex-start;
}
.chapters-page .subject-breadcrumb a{
  color: #1d4ed8;
  text-decoration: none;
}
.chapters-page .subject-breadcrumb a:hover{
  text-decoration: underline;
}
html[data-theme="dark"] .chapters-page .subject-breadcrumb{
  color: #94a3b8;
}
html[data-theme="dark"] .chapters-page .subject-breadcrumb a{
  color: #93c5fd;
}
html[data-theme="dark"] .chapters-page .subject-breadcrumb a:hover{
  color: #bfdbfe;
}
.chapters-page .page-head h1{
  margin: 0 0 .35rem;
  font-size: var(--fs-h1);            /* was 2rem */
  color: var(--bs-heading);
}
.chapters-page .page-sub{
  margin: 0;
  color: var(--bs-muted);
  font-size: var(--fs-sub);
}

.chapters{ padding: 1rem 0 2.5rem; }

.chapters-grid{
  display: grid;
  gap: 1rem;
  grid-template-columns: 1fr;         /* 1 column by default (mobile-first) */
}
/* keep single column on larger screens for now (your current behavior) */
@media (min-width: 768px){ .chapters-grid{ grid-template-columns: repeat(1, 1fr); } }
@media (min-width: 1000px){ .chapters-grid{ grid-template-columns: repeat(1, 1fr); } }

.chapter-card{
  background: var(--bs-surface);
  border: 1px solid var(--bs-border-color);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  transition: border-color .2s ease, box-shadow .2s ease, transform .18s ease;
  will-change: transform;
}
.chapter-card:hover{
  transform: translateY(-3px);
  box-shadow: var(--shadow);
  border-color: rgba(14,165,233,.45);
}
html[data-theme="dark"] .chapter-card:hover{ border-color: #60a5fa; }

/* Header row */
.card-head{
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: .75rem;
  padding: .85rem .9rem;
}

.chapter-title{
  margin: 0;
  font-size: var(--fs-card);          /* was 1.05rem */
  color: var(--bs-heading);
}

/* Toggle button (compact ghost style, with strong hover contrast) */
.toggle-topics{
  appearance: none;
  font: inherit;
  font-weight: 700;
  font-size: var(--fs-btn);           /* responsive size */
  padding: .45rem .7rem;
  border-radius: .5rem;
  border: 1px solid #c9d6e5;
  background: #ffffff;
  color: #0b1220;
  cursor: pointer;
  transition: background-color .15s ease, border-color .15s ease, box-shadow .15s ease, color .15s ease;
}
.toggle-topics .count{ font-weight: 600; opacity: .8; }
.toggle-topics:hover{
  background: #eef6ff;
  border-color: var(--bs-primary);
  box-shadow: 0 0 0 3px rgba(14,165,233,.18);
}

/* Dark mode toggle treatment */
html[data-theme="dark"] .toggle-topics{
  background: #0b1a2e;
  color: #f8fbff;
  border-color: #334155;
}
html[data-theme="dark"] .toggle-topics:hover{
  background: #0e253f;
  border-color: #60a5fa;
  box-shadow: 0 0 0 3px rgba(96,165,250,.28);
}

/* Collapsible panel */
.topics-panel{
  padding: 0 .9rem .9rem;
  overflow: hidden;
  max-height: 0;                  /* animated */
  opacity: 0;                     /* fade for crispness */
  transition: max-height .12s ease-out, opacity .12s ease-out;
}
.topics-panel.open{ opacity: 1; }

/* .chapter-card[data-collapsed="true"] .topics-panel{
  max-height controlled by JS
} */

.topics-list{
  list-style: none;
  padding: 0;
  margin: .25rem 0 0;
  display: grid;
  gap: .35rem;
  grid-template-columns: 1fr 1fr;     /* default: two columns on wider screens */
}

.topics-list li a{
  display: inline-block;
  padding: .35rem .5rem;
  border-radius: .4rem;
  text-decoration: none;
  color: var(--bs-body-color);
  border: 1px solid transparent;
  transition: background-color .15s ease, border-color .15s ease, color .15s ease;
  font-size: var(--fs-link);
}
.topics-list li a:hover{
  background: rgba(14,165,233,.10);
  border-color: rgba(14,165,233,.35);
  color: var(--bs-heading);
}

/* Empty states */
.empty-note, .no-topics{
  color: var(--bs-muted);
  padding: .75rem .9rem;
  margin: 0;
  font-size: var(--fs-sub);
}

/* --- Mobile tweaks: < 768px --- */
@media (max-width: 767.98px){
  .card-head{ padding: .7rem .75rem; gap: .5rem; }
  .toggle-topics{ padding: .4rem .6rem; font-weight: 600; }
  .topics-panel{ padding: 0 .75rem .75rem; }

  /* “OL grid” → assuming you meant the topics grid: force single column on small devices */
  .topics-list{ grid-template-columns: 1fr; }

  /* slightly tighter link padding on small devices */
  .topics-list li a{ padding: .32rem .45rem; }
}

/* Optional idea (keep commented if not needed):
@media (min-width: 900px){
  .chapters-grid{ grid-template-columns: repeat(2, 1fr); }
} */

/* Icon sizing & default visibility */
.toggle-topics .icon{
  width: 1.1em;
  height: 1.1em;
  display: none;
  vertical-align: -0.1em;
  color: #25a7c1;         /* drives fill via currentColor */
}
/* Swap icons based on state */
.toggle-topics[aria-expanded="true"]  .icon-show{ display: none; }
.toggle-topics[aria-expanded="true"]  .icon-hide{ display: inline-block; }
.toggle-topics[aria-expanded="false"] .icon-show{ display: inline-block; }
.toggle-topics[aria-expanded="false"] .icon-hide{ display: none; }

/* Mobile: show only icons (hide text & count for compact UI) */
/* Mobile: ≤ 480px shows only the icons */
@media (max-width: 768px){
  .toggle-topics{
    display: inline-flex;
    align-items: center;
    gap: .4rem;
    padding: .4rem .55rem;
  }
  .toggle-topics .label,
  .toggle-topics .count{
    position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
    overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
  }
  .toggle-topics .icon{ display: inline-block; }

  /* Swap icons only on small screens */
  .toggle-topics[aria-expanded="true"]  .icon-show{ display: none; }
  .toggle-topics[aria-expanded="true"]  .icon-hide{ display: inline-block; }
  .toggle-topics[aria-expanded="false"] .icon-show{ display: inline-block; }
  .toggle-topics[aria-expanded="false"] .icon-hide{ display: none; }
}
html[data-theme="dark"] .toggle-topics .icon{ color:#60a5fa; }




/* --- Chapter Description (Card & Book Intro Style) --- */
.chapter-description {
  padding: 1rem 0 2rem;
  width: 100%;
  box-sizing: border-box;
}

.chapter-description .container {
  /* Card Appearance */
  background-color: var(--bs-surface, #ffffff);
  border: 1px solid var(--bs-border-color, #e2e8f0);
  border-radius: var(--radius, 12px);
  box-shadow: var(--shadow-sm, 0 1px 3px rgba(0,0,0,0.08));

  /* Spacing & Layout */
  max-width: 1080px;       /* Slightly wider to feel like a "page" */
  margin-inline: auto;    /* Center the card itself */
  padding: 2rem;   /* Generous padding for "book" feel */
  
  /* Text Alignment */
  text-align: left;
}

/* Typography for "Book Intro" feel */
.chapter-description p {
  font-size: 1rem;
  line-height: 1.5;       /* Relaxed line height */
  color: var(--bs-body-color, #334155);
  margin-bottom: 1rem;
  max-width: 95%;        /* Readable line length constraint within the card */
}

/* First paragraph as a "Lead" */
.chapter-description p:first-of-type {
  font-size: 1rem;
  font-weight: 500;
  color: var(--bs-heading, #0f172a);
  margin-top: 0;
}

.chapter-description p:last-child {
  margin-bottom: 0;
}

/* Mobile Adjustments */
@media (max-width: 768px) {
  .chapter-description {
    padding: 1rem 0 1.5rem;
  }
  .chapter-description .container {
    padding: 1.5rem 1.25rem;
    border-radius: 8px;
    margin-inline: 1rem; /* Ensure card has space from edges */
    width: auto;
  }
  .chapter-description p {
    font-size: 1rem;
    line-height: 1.4;
    max-width: 100%; 
    text-align: left;
  }
  .chapter-description p:first-of-type {
    font-size: 1rem;
  }
}

/* Toggle expansion styles */
.chapter-description .read-more-link .btn-link {
  background: none;
  border: none;
  padding: 0;
  color: #0056b3 !important; /* Safe dark blue for strict accessibility compliance */
  font-weight: 500;
  cursor: pointer;
  text-decoration: underline;
  margin-left: 0.25rem;
  font-size: inherit;
  font-family: inherit;
}

.chapter-description .show-less-btn {
  background: none;
  border: 1.1px solid var(--bs-border-color, #e2e8f0);
  padding: 0.5rem 1rem;
  border-radius: 6px;
  color: var(--bs-body-color, #334155);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  margin: 0.25rem 0 0 auto;
  transition: all 0.5s;
}

.chapter-description .show-less-btn:hover {
  background-color: var(--bs-surface-hover, #f8fafc);
  border-color: var(--bs-border-color-hover, #cbd5e1);
}