/**
 * 功能：敬老版课程阅读器的布局、目录、进度与移动端抽屉样式。
 * 作者：Cursor
 * 日期：2026-08-25
 * 版本：1.0.0
 */

:root{
  --reader-topbar-h:82px;
  --reader-sidebar-w:340px;
  --paper:#fbfaf4;
  --paper-2:#f3f0e6;
  --card:#fffefa;
  --ink:#173d32;
  --ink-2:#31574b;
  --muted:#6f7f78;
  --forest:#234f40;
  --forest-dark:#173a2f;
  --sage:#7c9a84;
  --sage-soft:#e8efe8;
  --clay:#bd6955;
  --clay-soft:#f7e6df;
  --line:rgba(23,61,50,.15);
  --shadow:0 20px 54px rgba(35,79,64,.13);
  --serif:"Songti SC","STSong","Noto Serif SC",Georgia,serif;
  --sans:-apple-system,BlinkMacSystemFont,"PingFang SC","Segoe UI",sans-serif;
}

*{box-sizing:border-box}
html,body{width:100%;height:100%;margin:0}
html{background:var(--paper)}
body{
  overflow:hidden;
  color:var(--ink);
  background:var(--paper);
  font-family:var(--sans);
  -webkit-font-smoothing:antialiased;
}
button,a{font:inherit}
button{color:inherit}
a{color:inherit;text-decoration:none}
button:focus-visible,a:focus-visible{
  outline:4px solid rgba(189,105,85,.38);
  outline-offset:2px;
}
.sr-only{
  position:absolute!important;
  width:1px!important;
  height:1px!important;
  padding:0!important;
  margin:-1px!important;
  overflow:hidden!important;
  clip:rect(0,0,0,0)!important;
  white-space:nowrap!important;
  border:0!important;
}

/* 顶栏 */
.reader-topbar{
  position:fixed;
  inset:0 0 auto;
  z-index:80;
  height:var(--reader-topbar-h);
  padding:0 20px;
  display:flex;
  align-items:center;
  gap:14px;
  border-bottom:1px solid var(--line);
  background:rgba(251,250,244,.96);
  box-shadow:0 3px 18px rgba(35,79,64,.05);
  backdrop-filter:blur(18px);
}
.back-link,.catalog-button{
  min-height:48px;
  padding:0 15px;
  display:inline-flex;
  align-items:center;
  justify-content:center;
  gap:8px;
  flex:0 0 auto;
  border:1px solid var(--line);
  border-radius:13px;
  color:var(--ink-2);
  background:var(--card);
  font-size:16px;
  font-weight:780;
  cursor:pointer;
  transition:background .18s,border-color .18s,transform .18s;
}
.catalog-button{border-color:rgba(35,79,64,.28)}
.back-link:hover,.catalog-button:hover{
  border-color:rgba(35,79,64,.35);
  background:var(--sage-soft);
  transform:translateY(-1px);
}
.back-link svg,.catalog-button svg{width:20px;height:20px;flex:0 0 auto}
.reader-heading{
  min-width:120px;
  flex:1 1 auto;
  overflow:hidden;
}
.reader-kicker{
  color:var(--clay);
  font-size:12px;
  font-weight:820;
  letter-spacing:.08em;
}
.reader-title{
  margin-top:4px;
  overflow:hidden;
  text-overflow:ellipsis;
  white-space:nowrap;
  font:700 18px/1.3 var(--serif);
}
.font-controls{
  padding:4px;
  display:flex;
  align-items:center;
  gap:3px;
  flex:0 0 auto;
  border:1px solid var(--line);
  border-radius:13px;
  background:var(--card);
}
.font-controls>span{
  padding:0 7px;
  color:var(--muted);
  font-size:13px;
  font-weight:760;
}
.font-controls button{
  min-width:42px;
  height:40px;
  padding:0 8px;
  border:0;
  border-radius:9px;
  color:var(--ink-2);
  background:transparent;
  font-size:14px;
  font-weight:780;
  cursor:pointer;
}
.font-controls button:hover{background:var(--sage-soft)}
.font-controls button[aria-pressed="true"]{color:#fff;background:var(--forest)}
.progress-summary{
  width:138px;
  flex:0 0 auto;
}
.progress-copy{
  display:flex;
  align-items:baseline;
  justify-content:space-between;
  gap:8px;
  color:var(--muted);
  font-size:12px;
  font-weight:720;
}
.progress-copy strong{color:var(--forest);font-size:15px}
.progress-track{
  height:7px;
  margin-top:7px;
  overflow:hidden;
  border-radius:999px;
  background:#dfe6df;
}
.progress-track span{
  display:block;
  width:0;
  height:100%;
  border-radius:inherit;
  background:var(--forest);
  transition:width .32s ease;
}

/* 阅读区与目录 */
.reader-shell{
  height:100%;
  padding-top:var(--reader-topbar-h);
  display:grid;
  grid-template-columns:var(--reader-sidebar-w) minmax(0,1fr);
  transition:grid-template-columns .25s ease;
}
.reader-sidebar{
  min-width:0;
  min-height:0;
  display:flex;
  flex-direction:column;
  border-right:1px solid var(--line);
  background:var(--card);
  transition:transform .25s ease;
}
.sidebar-intro{
  padding:20px 22px 16px;
  border-bottom:1px solid var(--line);
}
.sidebar-intro strong{
  display:block;
  font:700 23px/1.35 var(--serif);
}
.sidebar-intro span{
  display:block;
  margin-top:6px;
  color:var(--muted);
  font-size:15px;
  line-height:1.55;
}
.chapter-tree{
  min-height:0;
  padding:12px 12px 36px;
  overflow-y:auto;
  overscroll-behavior:contain;
}
.chapter-tree::-webkit-scrollbar{width:7px}
.chapter-tree::-webkit-scrollbar-thumb{border-radius:8px;background:rgba(35,79,64,.2)}
.chapter{
  margin:5px 0;
  border:1px solid transparent;
  border-radius:15px;
}
.chapter.current{border-color:rgba(35,79,64,.14);background:rgba(232,239,232,.42)}
.chapter-toggle{
  width:100%;
  min-height:58px;
  padding:9px 10px;
  display:grid;
  grid-template-columns:36px minmax(0,1fr) auto 20px;
  align-items:center;
  gap:8px;
  border:0;
  border-radius:13px;
  background:transparent;
  text-align:left;
  cursor:pointer;
}
.chapter-toggle:hover{background:var(--sage-soft)}
.chapter-number{
  color:var(--clay);
  font:400 20px/1 Georgia,serif;
}
.chapter-name{
  min-width:0;
  font-size:16px;
  font-weight:820;
  line-height:1.4;
}
.chapter-count{
  padding:3px 8px;
  border-radius:999px;
  color:var(--muted);
  background:var(--paper-2);
  font-size:12px;
  font-weight:760;
  white-space:nowrap;
}
.chapter-caret{
  width:18px;
  height:18px;
  display:grid;
  place-items:center;
  color:var(--muted);
  transition:transform .2s ease;
}
.chapter-caret svg{width:16px;height:16px}
.chapter.collapsed .chapter-caret{transform:rotate(-90deg)}
.lesson-list{
  margin:0;
  padding:2px 7px 9px 17px;
  list-style:none;
}
.chapter.collapsed .lesson-list{display:none}
.lesson-link{
  min-height:52px;
  margin:2px 0;
  padding:8px 10px;
  display:grid;
  grid-template-columns:24px minmax(0,1fr);
  align-items:center;
  gap:9px;
  border:1px solid transparent;
  border-radius:12px;
  color:var(--ink-2);
  font-size:15px;
  font-weight:650;
  line-height:1.45;
}
.lesson-link:hover{color:var(--ink);background:var(--paper-2)}
.lesson-link.active{
  border-color:rgba(35,79,64,.22);
  color:var(--forest-dark);
  background:var(--sage-soft);
  font-weight:820;
}
.lesson-status{
  width:20px;
  height:20px;
  display:grid;
  place-items:center;
  border:2px solid rgba(49,87,75,.36);
  border-radius:50%;
  color:#fff;
  font-size:12px;
  font-weight:900;
}
.lesson-link.active .lesson-status{
  border-color:var(--forest);
  box-shadow:0 0 0 4px rgba(124,154,132,.16);
}
.lesson-link.active:not(.done) .lesson-status:after{
  content:"";
  width:8px;
  height:8px;
  border-radius:50%;
  background:var(--forest);
}
.lesson-link.done .lesson-status{
  border-color:var(--forest);
  background:var(--forest);
}
.lesson-link.done .lesson-status:after{content:"✓"}

.reader-content{
  min-width:0;
  min-height:0;
  display:flex;
  flex-direction:column;
  background:var(--paper-2);
}
.frame-area{
  min-height:0;
  flex:1 1 auto;
  position:relative;
  background:var(--paper);
}
.lesson-frame{
  position:absolute;
  inset:0;
  width:100%;
  height:100%;
  border:0;
  background:var(--paper);
}
.lesson-footer{
  min-height:94px;
  padding:12px 18px;
  display:grid;
  grid-template-columns:minmax(0,1fr) auto minmax(0,1fr);
  gap:12px;
  align-items:stretch;
  border-top:1px solid var(--line);
  background:var(--card);
}
.step-button,.complete-button{
  min-width:0;
  min-height:66px;
  border-radius:14px;
  cursor:pointer;
  transition:border-color .18s,background .18s,transform .18s,box-shadow .18s;
}
.step-button{
  padding:9px 16px;
  display:flex;
  align-items:center;
  gap:12px;
  border:1px solid var(--line);
  background:var(--paper);
}
.step-button.next{flex-direction:row-reverse;text-align:right}
.step-button:hover{
  border-color:rgba(35,79,64,.38);
  background:var(--sage-soft);
  transform:translateY(-1px);
}
.step-button.disabled{
  opacity:.38;
  pointer-events:none;
}
.step-arrow{flex:0 0 auto;color:var(--forest);font-size:30px;line-height:1}
.step-copy{min-width:0;display:flex;flex-direction:column;gap:3px}
.step-label{color:var(--muted);font-size:12px;font-weight:760}
.step-title{
  overflow:hidden;
  text-overflow:ellipsis;
  white-space:nowrap;
  font-size:15px;
  font-weight:800;
}
.complete-button{
  min-width:174px;
  padding:0 22px;
  border:2px solid var(--forest);
  color:#fff;
  background:var(--forest);
  box-shadow:0 7px 18px rgba(35,79,64,.18);
  font-size:16px;
  font-weight:850;
}
.complete-button:hover{
  background:var(--forest-dark);
  transform:translateY(-1px);
  box-shadow:0 10px 23px rgba(35,79,64,.22);
}
.complete-button:disabled{
  cursor:default;
  box-shadow:none;
  opacity:.78;
}
.complete-button:disabled:hover{
  background:var(--forest);
  transform:none;
}
.complete-button[aria-pressed="true"]:disabled{
  color:var(--forest);
  background:var(--sage-soft);
  opacity:1;
}
.complete-button[aria-pressed="true"]:not(:disabled){
  color:#fff;
  background:var(--forest);
}
.scrim{
  display:none;
  position:fixed;
  inset:var(--reader-topbar-h) 0 0;
  z-index:60;
  width:auto;
  height:auto;
  padding:0;
  border:0;
  background:rgba(17,38,31,.48);
  backdrop-filter:blur(3px);
  cursor:pointer;
}
.route-announcer{position:fixed}

/* 宽屏可收起目录。 */
@media(min-width:901px){
  html.sidebar-collapsed .reader-shell{grid-template-columns:0 minmax(0,1fr)}
  html.sidebar-collapsed .reader-sidebar{
    overflow:hidden;
    border-right:0;
    transform:translateX(-100%);
    pointer-events:none;
  }
}

/* 平板和手机默认使用抽屉，不挤占正文。 */
@media(max-width:900px){
  .reader-shell{
    display:flex;
    flex-direction:column;
  }
  .reader-content{
    flex:1 1 auto;
    min-height:0;
  }
  .reader-sidebar{
    position:fixed;
    z-index:70;
    top:var(--reader-topbar-h);
    bottom:0;
    left:0;
    width:min(var(--reader-sidebar-w),88vw);
    box-shadow:var(--shadow);
    transform:translateX(-105%);
  }
  body.drawer-open .reader-sidebar{transform:translateX(0)}
  body.drawer-open .scrim{display:block}
  .progress-summary{width:112px}
}

@media(max-width:720px){
  :root{--reader-topbar-h:164px;--reader-sidebar-w:340px}
  .reader-topbar{
    padding:10px 12px;
    display:grid;
    grid-template-columns:auto minmax(0,1fr) auto;
    grid-template-areas:
      "catalog heading back"
      "font font progress";
    align-content:center;
    gap:8px 10px;
  }
  .catalog-button{grid-area:catalog}
  .reader-heading{grid-area:heading}
  .back-link{grid-area:back}
  .font-controls{grid-area:font;width:max-content}
  .progress-summary{grid-area:progress;justify-self:end;width:112px}
  .reader-title{
    font-size:17px;
    white-space:normal;
    overflow:hidden;
    text-overflow:unset;
    display:-webkit-box;
    -webkit-box-orient:vertical;
    -webkit-line-clamp:2;
  }
}

@media(max-width:520px){
  .back-link,.catalog-button{
    min-height:46px;
    padding:0 11px;
    font-size:15px;
  }
  .back-link .button-copy{display:none}
  .reader-kicker{font-size:11px}
  .reader-title{font-size:16px}
  .font-controls>span{padding:0 5px;font-size:12px}
  .font-controls button{min-width:38px;height:38px;padding:0 5px;font-size:13px}
  .progress-copy{font-size:11px}
  .progress-copy strong{font-size:14px}
  .lesson-footer{
    min-height:0;
    padding:10px 12px;
    grid-template-columns:1fr 1fr;
    grid-template-areas:
      "previous next";
    gap:8px;
  }
  .lesson-footer:has(.complete-button:not(:disabled)){
    min-height:158px;
    grid-template-areas:
      "complete complete"
      "previous next";
  }
  .step-button{min-height:58px;padding:7px 10px}
  .step-button.prev{grid-area:previous}
  .step-button.next{grid-area:next}
  .complete-button{
    display:none;
    grid-area:complete;
    min-height:54px;
    min-width:0;
    width:100%;
  }
  .complete-button:not(:disabled){display:block}
  .step-title{
    font-size:14px;
    white-space:normal;
    overflow:hidden;
    text-overflow:unset;
    display:-webkit-box;
    -webkit-box-orient:vertical;
    -webkit-line-clamp:2;
  }
  .step-label{font-size:11px}
  .step-arrow{font-size:26px}
}

@media(max-width:380px){
  .catalog-button .button-copy{display:none}
  .reader-topbar{grid-template-columns:48px minmax(0,1fr) 48px}
  .font-controls button{min-width:35px}
  .progress-summary{width:98px}
}

@media(prefers-reduced-motion:reduce){
  *,*:before,*:after{
    scroll-behavior:auto!important;
    animation-duration:.001ms!important;
    animation-iteration-count:1!important;
    transition-duration:.001ms!important;
  }
}