:root{
  --ink:#1f2a28; --muted:#66736e; --faint:#8b9691;
  --paper:#f6f1e7; --paper-2:#efe8da; --card:#fffdf8; --line:#e1d8c7;
  --brand:#0f4f4a; --brand-2:#1a6a61; --brand-soft:#e3efec;
  --accent:#c26a35; --accent-soft:#fbeddf;
  --gold:#a9823f; --danger:#a13b32; --ok:#2f6b4f;
  --fs:17px; --radius:16px; --shadow:0 10px 30px rgba(31,42,40,.10);
  --serif:"Songti SC","Noto Serif SC","STSong",Georgia,serif;
  --sans:"PingFang SC","Hiragino Sans GB","Microsoft YaHei",-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;
}
[hidden]{display:none!important}
*{box-sizing:border-box}
html,body{height:100%;max-width:100%;overflow-x:hidden}
body{
  margin:0;color:var(--ink);font-family:var(--sans);font-size:var(--fs);line-height:1.65;
  background:
    radial-gradient(1200px 600px at 12% -10%, #fbf7ee 0%, transparent 60%),
    radial-gradient(900px 500px at 100% 0%, #eaf2ef 0%, transparent 55%),
    var(--paper);
}
button{font-family:inherit;font-size:inherit;color:inherit;cursor:pointer}
button:focus-visible,textarea:focus-visible,a:focus-visible{outline:3px solid #2f8f83;outline-offset:2px}
.app{height:100dvh;max-width:100vw;display:flex;flex-direction:column;overflow:hidden}
.topbar{
  height:68px;flex:0 0 68px;display:flex;align-items:center;gap:14px;padding:0 20px;
  background:rgba(255,253,248,.88);border-bottom:1px solid var(--line);
  backdrop-filter:blur(10px);position:relative;z-index:20;
}
.brand{display:flex;align-items:center;gap:12px;min-width:0;cursor:pointer;border-radius:12px}
.brand:hover .brand-mark{box-shadow:0 4px 16px rgba(15,79,74,.35)}
.brand-mark{
  width:42px;height:42px;border-radius:50%;display:grid;place-items:center;flex:0 0 auto;
  background:linear-gradient(145deg,var(--brand),#17665c);color:#fff;font-family:var(--serif);
  font-size:22px;box-shadow:0 4px 12px rgba(15,79,74,.26);
}
.brand-text{display:flex;flex-direction:column;line-height:1.25;min-width:0}
.brand-text strong{font-family:var(--serif);font-size:1.08em;letter-spacing:.02em;white-space:nowrap}
.brand-text span{color:var(--muted);font-size:.78em;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.top-course{display:flex;align-items:center;gap:8px;margin-left:10px;min-width:0}
.top-course span{font-size:.7em;letter-spacing:.12em;color:var(--faint);white-space:nowrap}
.top-course select{
  height:38px;max-width:230px;border:1px solid var(--line);border-radius:10px;
  background:var(--paper);color:var(--ink);font-family:inherit;font-size:.82em;
  padding:0 10px;outline:none;
}
.top-course select:focus{border-color:#9cc6bf;box-shadow:0 0 0 3px rgba(15,79,74,.1)}
.top-actions{margin-left:auto;display:flex;align-items:center;gap:10px}
.icon-btn{
  width:42px;height:42px;border-radius:12px;border:1px solid var(--line);background:var(--card);
  display:grid;place-items:center;font-size:.92em;transition:.15s;flex:0 0 auto;
}
.icon-btn:hover{background:var(--brand-soft);border-color:#bcd6d0}
.fontctl{display:flex;gap:4px}
.ghost-btn{
  min-height:42px;padding:0 14px;border-radius:12px;border:1px solid var(--line);
  background:transparent;color:var(--ink);font-size:.86em;transition:.15s;
}
.ghost-btn:hover{background:var(--card);border-color:#c8bdab}
.switch{display:flex;align-items:center;gap:7px;font-size:.82em;color:var(--muted);user-select:none;min-height:42px}
.switch input{width:18px;height:18px;accent-color:var(--brand)}
.only-mobile{display:none}

.layout{flex:1;display:grid;grid-template-columns:312px minmax(0,1fr);min-height:0}
.sidebar{
  border-right:1px solid var(--line);background:rgba(247,243,234,.72);
  padding:18px 16px 24px;overflow-y:auto;min-height:0;
}
.side-card{
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:16px;box-shadow:0 4px 16px rgba(31,42,40,.05);
}
.course-kicker{font-size:.72em;letter-spacing:.14em;color:var(--gold);text-transform:uppercase}
.course-card h2{font-family:var(--serif);font-size:1.75em;margin:4px 0 6px;letter-spacing:.04em}
.course-stats{color:var(--muted);font-size:.82em;line-height:1.7}
.course-picker{
  display:flex;flex-direction:column;gap:5px;margin-top:12px;color:var(--faint);
  font-size:.7em;letter-spacing:.08em;
}
.course-picker select{
  width:100%;min-height:40px;border:1px solid var(--line);border-radius:10px;
  background:var(--paper);color:var(--ink);font-family:inherit;font-size:1.25em;
  padding:6px 10px;outline:none;
}
.course-picker select:focus{border-color:#9cc6bf;box-shadow:0 0 0 3px rgba(15,79,74,.1)}
.course-actions{display:flex;gap:8px;margin-top:12px}
.small-btn{
  min-height:38px;padding:0 12px;border-radius:10px;border:1px solid var(--line);
  background:var(--brand-soft);color:var(--brand);font-size:.8em;font-weight:600;
}
.small-btn:hover{background:#d5e7e2}
.side-sec{margin-top:22px}
.side-title{
  display:flex;justify-content:space-between;align-items:center;color:var(--muted);
  font-size:.76em;letter-spacing:.12em;margin:0 4px 10px;text-transform:uppercase;
}
.outline{display:flex;flex-direction:column;gap:6px}
.chapter{border:1px solid transparent;border-radius:12px;overflow:hidden}
.chapter.open{background:var(--card);border-color:var(--line)}
.chapter-head{
  width:100%;display:flex;align-items:center;gap:9px;padding:10px 9px;background:transparent;border:0;
  text-align:left;border-radius:12px;font-size:.86em;font-weight:600;color:var(--ink);
}
.chapter-head:hover{background:var(--paper-2)}
.chapter-head .no{
  flex:0 0 auto;width:26px;height:26px;border-radius:8px;background:var(--brand);color:#fff;
  display:grid;place-items:center;font-size:.72em;font-weight:700;
}
.chapter-head .name{flex:1;min-width:0;line-height:1.35}
.chapter-head .caret{color:var(--faint);font-size:.8em;transition:.15s}
.chapter.open .caret{transform:rotate(90deg)}
.sections{display:none;padding:0 8px 10px 43px;flex-direction:column;gap:3px}
.chapter.open .sections{display:flex}
.section-row{display:flex;align-items:center;gap:6px;border-radius:8px}
.section-btn{
  flex:1;text-align:left;border:0;background:transparent;border-radius:8px;padding:7px 8px;
  font-size:.8em;color:var(--muted);line-height:1.45;
}
.section-btn:hover,.section-btn.active{background:var(--brand-soft);color:var(--brand)}
.sum-btn{
  flex:0 0 auto;border:0;background:transparent;color:var(--faint);font-size:.72em;padding:5px 6px;border-radius:6px;
}
.sum-btn:hover{background:var(--accent-soft);color:var(--accent)}
.side-note{
  margin-top:20px;border-left:3px solid var(--gold);background:#fbf6e9;border-radius:0 12px 12px 0;
  padding:12px 14px;color:#6c5a35;font-size:.78em;
}
.side-note strong{display:block;margin-bottom:4px;color:#5a4721}
.side-note p{margin:0;line-height:1.6}

.chat{display:flex;flex-direction:column;min-width:0;min-height:0;position:relative}
.chat-head{
  flex:0 0 auto;display:flex;align-items:center;justify-content:space-between;gap:12px;
  padding:18px 34px 12px;
}
.chat-title{font-family:var(--serif);font-size:1.3em;font-weight:700;letter-spacing:.03em}
.chat-sub{color:var(--muted);font-size:.8em;margin-top:2px}
.head-right{display:flex;align-items:center;gap:7px;color:var(--muted);font-size:.78em;white-space:nowrap}
.status-dot{width:8px;height:8px;border-radius:50%;background:#c9c1b1;box-shadow:0 0 0 4px rgba(201,193,177,.18)}
.status-dot.on{background:#3a8b63;box-shadow:0 0 0 4px rgba(58,139,99,.15)}
.status-dot.err{background:var(--danger);box-shadow:0 0 0 4px rgba(161,59,50,.14)}

.messages{
  flex:1;overflow-y:auto;padding:8px 34px 30px;scroll-behavior:smooth;
}
.wrap{max-width:900px;margin:0 auto}
.welcome{
  background:linear-gradient(160deg,#fffdf8 0%,#fbf5e9 100%);
  border:1px solid var(--line);border-radius:24px;padding:28px 30px;box-shadow:var(--shadow);
  position:relative;overflow:hidden;margin:12px 0 24px;
}
.welcome:after{
  content:"碁";position:absolute;right:22px;top:-14px;font-family:var(--serif);font-size:150px;
  color:rgba(15,79,74,.055);line-height:1;pointer-events:none;
}
.welcome .eyebrow{font-size:.72em;letter-spacing:.18em;color:var(--gold);text-transform:uppercase}
.welcome h1{font-family:var(--serif);font-size:1.9em;line-height:1.35;margin:8px 0 10px;letter-spacing:.02em}
.welcome p{color:var(--muted);margin:0 0 18px;font-size:.9em;max-width:640px}
.suggests{display:grid;grid-template-columns:1fr 1fr;gap:10px;position:relative;z-index:1}
.suggest{
  text-align:left;border:1px solid var(--line);background:var(--card);border-radius:14px;
  padding:12px 14px;font-size:.86em;line-height:1.45;transition:.15s;color:var(--ink);
}
.suggest:hover{border-color:#b9d4ce;background:var(--brand-soft);transform:translateY(-1px)}
.suggest span{display:block;color:var(--faint);font-size:.82em;margin-top:3px}

.row{display:flex;gap:12px;margin:0 0 22px;align-items:flex-start}
.row.user{flex-direction:row-reverse}
.avatar{
  flex:0 0 38px;width:38px;height:38px;border-radius:50%;display:grid;place-items:center;
  font-family:var(--serif);font-size:1.02em;background:var(--brand);color:#fff;box-shadow:0 3px 10px rgba(15,79,74,.2);
}
.row.user .avatar{background:var(--accent);box-shadow:0 3px 10px rgba(194,106,53,.2)}
.bubble-wrap{max-width:min(760px,86%);min-width:0}
.row.user .bubble-wrap{max-width:min(620px,80%)}
.name-line{font-size:.72em;color:var(--faint);margin:0 0 5px 3px;letter-spacing:.04em}
.row.user .name-line{text-align:right;margin-right:3px}
.bubble{
  background:var(--card);border:1px solid var(--line);border-radius:6px 18px 18px 18px;
  padding:14px 18px;box-shadow:0 3px 12px rgba(31,42,40,.05);font-size:.95em;line-height:1.75;
  overflow-wrap:break-word;
}
.row.user .bubble{background:var(--brand);color:#fff;border-color:var(--brand);border-radius:18px 6px 18px 18px}
.bubble p{margin:0 0 .55em}
.bubble p:last-child{margin-bottom:0}
.bubble ol,.bubble ul{margin:.2em 0 .7em;padding-left:1.4em}
.bubble li{margin:.18em 0}
.bubble strong{color:var(--brand)}
.row.user .bubble strong{color:#fff}
.bubble .cite{
  display:inline-flex;align-items:center;justify-content:center;min-width:22px;height:22px;
  margin:0 2px;padding:0 5px;border-radius:7px;border:0;background:var(--brand-soft);color:var(--brand);
  font-size:.7em;font-weight:700;vertical-align:1px;
}
.bubble .cite:hover{background:var(--brand);color:#fff}
.badge{
  display:inline-block;padding:2px 9px;border-radius:999px;background:var(--accent-soft);
  color:var(--accent);font-size:.68em;font-weight:600;letter-spacing:.03em;vertical-align:1px;
}
.badge.refuse{background:#f6e7e3;color:var(--danger)}
.badge.retrieval{background:#eef0e6;color:#5b6641}

.typing{display:inline-flex;gap:4px;align-items:center;height:20px}
.typing i{width:6px;height:6px;border-radius:50%;background:var(--faint);animation:blink 1.2s infinite}
.typing i:nth-child(2){animation-delay:.18s}.typing i:nth-child(3){animation-delay:.36s}
@keyframes blink{0%,80%,100%{opacity:.25;transform:translateY(0)}40%{opacity:1;transform:translateY(-2px)}}

.answer-tools{display:flex;align-items:center;gap:6px;margin-top:7px;flex-wrap:wrap}
.tool{
  border:1px solid transparent;background:transparent;color:var(--faint);font-size:.72em;
  padding:5px 8px;border-radius:8px;
}
.tool:hover{background:var(--card);border-color:var(--line);color:var(--brand)}
.tool.on{background:var(--brand-soft);color:var(--brand)}

.cites{margin-top:10px;display:grid;grid-template-columns:1fr 1fr;gap:9px}
.cite-loading{
  grid-column:1/-1;display:flex;align-items:center;gap:8px;padding:10px 12px;
  border:1px dashed var(--line);border-radius:12px;background:var(--paper-2);
  color:var(--faint);font-size:.78em;
}
.cite-loading i{
  width:8px;height:8px;border-radius:50%;background:var(--brand);
  animation:citePulse 1s ease-in-out infinite;
}
@keyframes citePulse{50%{opacity:.25}}
.cite-card{
  display:flex;gap:10px;align-items:stretch;text-align:left;border:1px solid var(--line);
  background:var(--card);border-radius:13px;padding:8px;transition:.15s;min-width:0;
}
.cite-card:hover{border-color:#b9d4ce;box-shadow:0 4px 14px rgba(31,42,40,.07);transform:translateY(-1px)}
.cite-thumb{
  flex:0 0 84px;width:84px;height:62px;border-radius:9px;object-fit:cover;background:var(--paper-2);
}
.cite-main{min-width:0;flex:1;padding:1px 2px}
.cite-top{display:flex;align-items:center;gap:6px;color:var(--faint);font-size:.66em}
.cite-no{
  display:inline-grid;place-items:center;min-width:20px;height:20px;padding:0 4px;border-radius:6px;
  background:var(--brand);color:#fff;font-size:.9em;font-weight:700;
}
.cite-name{
  font-size:.82em;font-weight:600;line-height:1.35;margin:3px 0 2px;
  display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden;
}
.cite-pos{color:var(--muted);font-size:.68em;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.cite-time{color:var(--accent);font-size:.7em;margin-top:2px;font-variant-numeric:tabular-nums}

.refusal-box{
  border:1px solid #e8cfc7;background:#fdf4f1;border-radius:14px;padding:14px 16px;
}
.refusal-box .ref-kicker{color:var(--danger);font-size:.72em;font-weight:700;letter-spacing:.08em;margin-bottom:5px}
.refusal-box p{margin:0 0 .5em}
.refusal-box .sugs{display:flex;flex-wrap:wrap;gap:6px;margin-top:8px}
.chip-sug{
  border:1px solid #e3c9be;background:#fff;border-radius:999px;padding:6px 11px;font-size:.76em;color:#7a4a31;
}
.chip-sug:hover{background:var(--accent-soft)}

.composer-wrap{
  flex:0 0 auto;padding:0 34px 16px;background:linear-gradient(to top,var(--paper) 70%,rgba(246,241,231,0));
}
.composer-wrap > *{max-width:900px;margin-left:auto;margin-right:auto}
.context-chip{
  display:flex;align-items:center;gap:8px;margin-bottom:8px;background:var(--brand-soft);
  border:1px solid #c4ddd7;color:var(--brand);border-radius:10px;padding:7px 11px;font-size:.78em;
}
.context-chip span{flex:1}
.context-chip button{border:0;background:transparent;color:var(--brand);font-size:1.05em;line-height:1}
.modes{display:flex;gap:6px;margin-bottom:9px;flex-wrap:wrap}
.mode-chip{
  border:1px solid var(--line);background:rgba(255,253,248,.7);border-radius:999px;
  padding:7px 13px;font-size:.78em;color:var(--muted);min-height:36px;
}
.mode-chip.active{background:var(--brand);border-color:var(--brand);color:#fff}
.mode-chip:hover:not(.active){background:var(--brand-soft)}
.composer{
  display:flex;align-items:flex-end;gap:8px;background:var(--card);border:1px solid var(--line);
  border-radius:20px;padding:9px 10px;box-shadow:0 8px 26px rgba(31,42,40,.09);
}
.composer:focus-within{border-color:#9cc6bf;box-shadow:0 8px 30px rgba(15,79,74,.12)}
.composer textarea{
  flex:1;border:0;background:transparent;resize:none;font:inherit;font-size:.95em;line-height:1.55;
  padding:9px 6px;max-height:150px;min-height:42px;color:var(--ink);outline:none;
}
.composer textarea::placeholder{color:#a3ada8}
.mic{width:42px;height:42px;border-radius:50%;border:0;background:var(--paper-2);font-size:1.02em}
.mic.rec{background:#f7ddd4;animation:pulse 1.4s infinite}
@keyframes pulse{0%,100%{box-shadow:0 0 0 0 rgba(194,106,53,.25)}50%{box-shadow:0 0 0 8px rgba(194,106,53,0)}}
.send-btn{
  min-width:76px;height:44px;border-radius:13px;border:0;background:var(--brand);color:#fff;
  font-weight:600;font-size:.88em;padding:0 16px;
}
.send-btn:hover{background:var(--brand-2)}
.send-btn:disabled{opacity:.5;cursor:not-allowed}
.send-btn.stop{background:var(--danger)}
.composer-foot{
  display:flex;justify-content:space-between;gap:10px;color:var(--faint);font-size:.68em;margin-top:7px;padding:0 4px;
}

/* 课程列表首页 */
.home{flex:1;overflow-y:auto;padding:44px 34px 64px}
.home-inner{max-width:1100px;margin:0 auto}
.home-hero{max-width:820px;margin:6px 0 6px}
.home-hero .eyebrow{font-size:.72em;letter-spacing:.18em;color:var(--gold);text-transform:uppercase}
.home-hero h1{font-family:var(--serif);font-size:clamp(2em,4.6vw,3.35em);line-height:1.28;margin:10px 0 12px;letter-spacing:.02em}
.home-hero p{color:var(--muted);font-size:.95em;max-width:680px;margin:0 0 14px}
.home-stats{color:var(--faint);font-size:.8em;letter-spacing:.04em}
.home-tools{display:flex;flex-direction:column;gap:10px;margin-top:20px;max-width:760px}
.course-search{
  width:min(430px,100%);height:44px;border:1px solid var(--line);border-radius:12px;
  background:var(--card);color:var(--ink);font-family:inherit;font-size:.9em;padding:0 14px;outline:none;
}
.course-search:focus{border-color:#9cc6bf;box-shadow:0 0 0 3px rgba(15,79,74,.1)}
.course-search::placeholder{color:var(--faint)}
.series-tabs{display:flex;flex-wrap:wrap;gap:7px}
.series-tab{
  border:1px solid var(--line);background:rgba(255,253,248,.75);border-radius:999px;
  min-height:34px;padding:5px 12px;font-size:.76em;color:var(--muted);
}
.series-tab:hover{background:var(--brand-soft)}
.series-tab.active{background:var(--brand);border-color:var(--brand);color:#fff}
.course-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px;margin-top:30px}
.course-tile{
  text-align:left;background:var(--card);border:1px solid var(--line);border-radius:22px;
  overflow:hidden;display:flex;flex-direction:column;padding:0;transition:.18s;box-shadow:0 4px 16px rgba(31,42,40,.04);
}
.course-tile:hover{transform:translateY(-3px);border-color:#b9d4ce;box-shadow:0 14px 36px rgba(31,42,40,.12)}
.tile-cover{position:relative;aspect-ratio:16/9;background:linear-gradient(135deg,#e8eee9,#f6f1e7);overflow:hidden}
.tile-cover img{width:100%;height:100%;object-fit:cover;display:block;transition:.25s}
.course-tile:hover .tile-cover img{transform:scale(1.03)}
.tile-code{
  position:absolute;left:12px;top:12px;background:rgba(15,79,74,.92);color:#fff;
  padding:3px 10px;border-radius:999px;font-size:.7em;letter-spacing:.08em;
}
.tile-body{padding:17px 20px 20px;display:flex;flex-direction:column;gap:7px;flex:1}
.tile-series{font-size:.7em;letter-spacing:.12em;color:var(--gold);text-transform:uppercase}
.tile-body h3{font-family:var(--serif);font-size:1.5em;margin:0;letter-spacing:.02em;line-height:1.3}
.tile-stats{font-size:.8em;color:var(--muted)}
.tile-desc{font-size:.83em;color:var(--muted);line-height:1.65;margin:0;
  display:-webkit-box;-webkit-line-clamp:3;-webkit-box-orient:vertical;overflow:hidden}
.tile-enter{
  margin-top:auto;padding-top:12px;color:var(--brand);font-size:.82em;font-weight:700;
  display:flex;align-items:center;gap:6px;
}
.course-tile:hover .tile-enter{color:var(--accent)}
.home-note{margin:28px 0 0;color:var(--faint);font-size:.72em;line-height:1.6}
@media (min-width:1200px){
  .course-grid{grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}
  .tile-body h3{font-size:1.32em}
}

/* modal / drawer */
.modal,.drawer{position:fixed;inset:0;z-index:80;display:grid;place-items:center}
.modal[hidden],.drawer[hidden]{display:none}
.modal-mask,.drawer-mask{position:absolute;inset:0;background:rgba(24,34,32,.45);backdrop-filter:blur(3px)}
.modal-panel{
  position:relative;background:var(--card);border-radius:22px;box-shadow:0 24px 70px rgba(0,0,0,.3);
  width:min(860px,calc(100vw - 32px));max-height:calc(100dvh - 56px);display:flex;flex-direction:column;overflow:hidden;
}
.modal-head{display:flex;justify-content:space-between;align-items:flex-start;gap:12px;padding:18px 20px 10px}
.modal-kicker{font-size:.7em;letter-spacing:.16em;color:var(--gold);text-transform:uppercase}
.modal-head h3{font-family:var(--serif);font-size:1.22em;margin:3px 0 0;line-height:1.4}
.video-panel{width:min(980px,calc(100vw - 32px))}
.video-panel video{width:100%;max-height:min(62vh,560px);background:#111;display:block}
.video-foot{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:11px 18px 16px;color:var(--muted);font-size:.8em}
.drawer{justify-items:end}
.drawer-panel{
  position:relative;width:min(560px,calc(100vw - 20px));height:100dvh;background:var(--card);
  box-shadow:-20px 0 60px rgba(0,0,0,.24);display:flex;flex-direction:column;
  animation:slidein .22s ease-out;
}
@keyframes slidein{from{transform:translateX(30px);opacity:.4}to{transform:none;opacity:1}}
.drawer-body{padding:4px 22px 30px;overflow-y:auto}
.drawer-body h4{font-family:var(--serif);font-size:1em;margin:18px 0 6px;color:var(--brand)}
.drawer-body p{margin:0 0 10px;font-size:.9em;line-height:1.75;color:#33413d}
.drawer-body ul,.drawer-body ol{padding-left:1.3em;margin:.2em 0 .9em;font-size:.9em}
.drawer-body li{margin:.25em 0}
.kp-meta{display:flex;flex-wrap:wrap;gap:6px;margin:2px 0 12px}
.tag{display:inline-block;padding:2px 9px;border-radius:999px;background:var(--paper-2);color:var(--muted);font-size:.72em}
.tag.p{background:var(--brand-soft);color:var(--brand)}
.tag.d{background:var(--accent-soft);color:var(--accent)}
.kp-actions{display:flex;gap:8px;margin:10px 0 4px;flex-wrap:wrap}
.kp-quote{border-left:3px solid var(--gold);background:#fbf6e9;padding:9px 12px;border-radius:0 10px 10px 0;font-size:.84em;color:#6c5a35}
.evidence{font-size:.82em;color:var(--muted);border-top:1px dashed var(--line);padding-top:8px;margin-top:12px}
.related{display:flex;flex-wrap:wrap;gap:6px}
.related button{border:1px solid var(--line);background:var(--paper);border-radius:999px;padding:5px 10px;font-size:.74em}
.related button:hover{background:var(--brand-soft)}
.graph-panel{width:min(1100px,calc(100vw - 24px))}
.graph-legend{display:flex;gap:16px;align-items:center;padding:0 22px 8px;font-size:.75em;color:var(--muted);flex-wrap:wrap}
.graph-legend .dot{width:10px;height:10px;border-radius:50%;display:inline-block;margin-right:4px}
.graph-legend .key{background:var(--accent)}.graph-legend .hard{background:var(--brand)}.graph-legend .normal{background:#a9b6b1}
.graph-legend .muted{color:var(--faint)}
.graph-scroll{overflow:auto;padding:0 16px 18px}
#graphSvg{display:block;min-width:900px}
.help-panel{width:min(680px,calc(100vw - 28px))}
.help-body h4{margin-top:16px}
.muted{color:var(--faint)}

.toast{
  position:fixed;left:50%;bottom:28px;transform:translate(-50%,20px);opacity:0;pointer-events:none;
  background:#24322f;color:#fff;padding:10px 16px;border-radius:12px;font-size:.82em;z-index:120;
  transition:.2s;max-width:min(460px,90vw);text-align:center;
}
.toast.show{opacity:1;transform:translate(-50%,0)}
.loading-line{height:2px;background:linear-gradient(90deg,transparent,var(--brand),transparent);background-size:200% 100%;animation:slide 1.4s infinite}
@keyframes slide{to{background-position:-200% 0}}

/* ---------- mobile shell (hidden outside <=620px) ---------- */
.mobile-only{display:none}
body.layer-open{overflow:hidden}
.sidebar-mask{display:none}
.sheet{
  display:none;position:fixed;inset:0;z-index:100;align-items:flex-end;justify-content:center;
}
.sheet-mask{position:absolute;inset:0;background:rgba(24,34,32,.48);backdrop-filter:blur(3px)}
.sheet-panel{
  position:relative;width:min(560px,100%);max-height:88dvh;background:var(--card);
  border-radius:22px 22px 0 0;box-shadow:0 -18px 60px rgba(0,0,0,.28);
  display:flex;flex-direction:column;overflow:hidden;
  padding-bottom:env(safe-area-inset-bottom,0px);animation:sheet-up .22s ease-out;
}
@keyframes sheet-up{from{transform:translateY(24px);opacity:.5}to{transform:none;opacity:1}}
.sheet-head{
  display:flex;align-items:flex-start;justify-content:space-between;gap:12px;
  padding:16px 18px 8px;flex:0 0 auto;
}
.sheet-head h3{font-family:var(--serif);font-size:1.2em;margin:3px 0 0;line-height:1.4}
.sheet-head .icon-btn{width:44px;height:44px}
.sheet-body{
  padding:6px 18px 18px;overflow-y:auto;
  min-height:0;flex:1;overscroll-behavior:contain;
}
.sheet-search{width:100%;height:44px}
.sheet-tabs{
  display:flex;gap:6px;overflow-x:auto;padding:10px 0 4px;
  scrollbar-width:none;-webkit-overflow-scrolling:touch;
}
.sheet-tabs::-webkit-scrollbar{display:none}
.sheet-tab{
  flex:0 0 auto;min-height:44px;padding:6px 13px;border:1px solid var(--line);border-radius:999px;
  background:rgba(255,253,248,.75);color:var(--muted);font-size:.78em;white-space:nowrap;
}
.sheet-tab.active{background:var(--brand);border-color:var(--brand);color:#fff}
.sheet-course-list{display:flex;flex-direction:column;gap:8px;margin-top:10px}
.sheet-course{
  display:flex;align-items:center;gap:10px;width:100%;min-height:60px;padding:10px 12px;
  text-align:left;border:1px solid var(--line);border-radius:14px;background:var(--card);color:var(--ink);
}
.sheet-course.active{border-color:var(--brand);background:var(--brand-soft);box-shadow:inset 0 0 0 1px var(--brand)}
.sheet-course-code{
  flex:0 0 auto;min-width:46px;padding:3px 7px;border-radius:8px;background:var(--paper-2);
  color:var(--brand);font-size:.72em;font-weight:700;text-align:center;letter-spacing:.04em;
}
.sheet-course.active .sheet-course-code{background:var(--brand);color:#fff}
.sheet-course-main{display:flex;flex-direction:column;gap:2px;min-width:0;flex:1}
.sheet-course-main strong{
  font-family:var(--serif);font-size:1.02em;line-height:1.35;
  white-space:nowrap;overflow:hidden;text-overflow:ellipsis;
}
.sheet-course-main small{
  color:var(--muted);font-size:.72em;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;
}
.sheet-course-check{
  flex:0 0 auto;width:24px;height:24px;border-radius:50%;display:grid;place-items:center;
  color:#fff;font-size:.78em;font-weight:700;
}
.sheet-course.active .sheet-course-check{background:var(--brand)}
.sheet-empty{padding:20px 2px;color:var(--faint);font-size:.85em;text-align:center}
.sheet-note{margin:12px 0 2px;color:var(--faint);font-size:.74em;line-height:1.6}
.more-list{display:flex;flex-direction:column;gap:8px}
.more-item{
  display:flex;flex-direction:column;align-items:flex-start;gap:1px;min-height:56px;
  padding:9px 14px;border:1px solid var(--line);border-radius:14px;background:var(--card);
  text-align:left;color:var(--ink);
}
.more-item span{font-weight:600;font-size:.92em}
.more-item small{color:var(--muted);font-size:.72em}
.more-item:hover{background:var(--brand-soft);border-color:#c4ddd7}
.more-row{
  display:flex;align-items:center;justify-content:space-between;gap:12px;min-height:56px;
  padding:9px 14px;border:1px solid var(--line);border-radius:14px;background:var(--card);
}
.more-label{font-weight:600;font-size:.9em}
.more-font{display:flex;align-items:center;gap:8px}
.more-font-btn{
  min-width:48px;height:44px;border:1px solid var(--line);border-radius:12px;
  background:var(--paper);color:var(--ink);font-size:.86em;font-weight:600;
}
.more-font-btn:hover{background:var(--brand-soft)}
.more-font-value{min-width:38px;text-align:center;color:var(--muted);font-size:.76em;font-variant-numeric:tabular-nums}
.more-switch{
  display:flex;align-items:center;gap:12px;min-height:60px;padding:9px 14px;
  border:1px solid var(--line);border-radius:14px;background:var(--card);cursor:pointer;
}
.more-switch input{width:22px;height:22px;flex:0 0 auto;accent-color:var(--brand)}
.more-switch-text{display:flex;flex-direction:column;gap:1px}
.more-switch-text strong{font-size:.92em}
.more-switch-text small{color:var(--muted);font-size:.72em}
.mode-sheet-grid{display:grid;grid-template-columns:1fr 1fr;gap:8px;padding:4px 0}
.mode-sheet-grid .mode-chip{
  min-height:50px;border-radius:14px;font-size:.86em;display:inline-flex;align-items:center;justify-content:center;
}

@media (max-width:980px){
  .layout{grid-template-columns:1fr}
  .sidebar{
    position:fixed;left:0;top:68px;bottom:0;width:min(340px,88vw);z-index:50;
    transform:translateX(-102%);transition:.22s;box-shadow:18px 0 40px rgba(0,0,0,.18);
  }
  .sidebar.open{transform:none}
  .only-mobile{display:grid}
  .chat-head,.messages{padding-left:18px;padding-right:18px}
  .composer-wrap{padding-left:14px;padding-right:14px}
  .cites{grid-template-columns:1fr}
  .suggests{grid-template-columns:1fr}
  .welcome{padding:22px}
  .welcome h1{font-size:1.55em}
  .brand-text span{display:none}
  .top-actions .ghost-btn{padding:0 10px}
  .switch span{display:none}
  .home{padding:28px 18px 40px}
  .home-tools{margin-top:16px}
  .course-search{width:100%}
  .course-grid{grid-template-columns:1fr;gap:14px}
  .home-hero h1{font-size:2em}
}
@media (max-width:620px){
  .topbar{padding:0 6px;gap:4px;height:60px;flex:0 0 60px}
  .brand{gap:0}
  .brand-text{display:none}
  .brand-mark{width:34px;height:34px;font-size:17px}
  .top-course{margin-left:2px}
  .top-course span{display:none}
  .top-course select{max-width:150px;height:36px;font-size:.72em;padding:0 4px}
  #homeBtn{display:none}
  .top-actions{gap:4px}
  .fontctl .icon-btn{width:30px;height:34px;font-size:.72em}
  #newBtn{width:38px;min-width:38px;padding:0;font-size:0}
  #newBtn::before{content:"＋";font-size:18px;line-height:1;font-weight:600}
  .top-actions{gap:3px}
  .fontctl{gap:2px}
  .fontctl .icon-btn{width:34px;height:34px;font-size:.76em}
  .switch{min-height:34px;gap:4px}
  #helpBtn{display:none}
  .ghost-btn{min-height:36px;padding:0 7px;font-size:.7em}
  .brand-mark{width:36px;height:36px;font-size:18px}
  .brand-text strong{font-size:.92em}
  .ghost-btn{font-size:.76em;min-height:38px;padding:0 8px}
  .fontctl .icon-btn{width:38px;height:38px}
  .chat-head{padding-top:12px}
  .chat-sub{display:none}
  .messages{padding-bottom:18px}
  .bubble{padding:12px 14px}
  .row{gap:9px}
  .avatar{width:34px;height:34px;flex-basis:34px;font-size:.9em}
  .bubble-wrap{max-width:88%}
  .cite-thumb{flex-basis:72px;width:72px;height:54px}
  .send-btn{min-width:60px;padding:0 11px}
  .composer-foot span:first-child{max-width:75%;line-height:1.4}
}

/* 移动壳层：手机与竖屏平板（<=980px）；>=981px 桌面完全保持 */
@media (max-width:980px){
  /* 顶栏：安全区 + 三入口（菜单 / 课程 / 更多） */
  .topbar{
    height:calc(60px + env(safe-area-inset-top,0px));
    flex:0 0 calc(60px + env(safe-area-inset-top,0px));
    padding:env(safe-area-inset-top,0px) 8px 0;
    gap:8px;
  }
  .brand,
  .top-course,
  .top-actions .fontctl,
  .top-actions .switch,
  #homeBtn,#helpBtn,#newBtn{display:none}
  .top-actions{margin-left:0;gap:0}
  #menuBtn,#moreBtn{
    width:44px;height:44px;min-width:44px;border-radius:13px;font-size:1.08em;background:var(--card);
  }
  #menuBtn{display:grid}
  #moreBtn{display:grid}
  .mobile-course-btn{
    display:flex;align-items:center;gap:7px;flex:1 1 auto;min-width:0;height:44px;
    padding:0 10px;border:1px solid var(--line);border-radius:13px;background:var(--card);
    text-align:left;overflow:hidden;
  }
  .mobile-course-kicker{flex:0 0 auto;color:var(--faint);font-size:.68em;letter-spacing:.08em}
  #mobileCourseName{
    flex:1;min-width:0;font-family:var(--serif);font-weight:700;font-size:.95em;
    white-space:nowrap;overflow:hidden;text-overflow:ellipsis;
  }
  .mobile-course-caret{flex:0 0 auto;color:var(--faint);font-size:.7em}

  /* 抽屉：遮罩 + 顶栏/安全区定位 + 隐藏聊天区重复目录按钮 */
  .sidebar{
    top:calc(60px + env(safe-area-inset-top,0px));z-index:52;
    padding-bottom:calc(20px + env(safe-area-inset-bottom,0px));
  }
  #sidebarMask:not([hidden]){
    display:block;position:fixed;left:0;right:0;
    top:calc(60px + env(safe-area-inset-top,0px));bottom:0;z-index:51;
    background:rgba(24,34,32,.42);backdrop-filter:blur(2px);animation:fadein .18s;
  }
  @keyframes fadein{from{opacity:0}to{opacity:1}}
  #sideToggle{display:none}

  /* 底部面板 */
  .sheet:not([hidden]){display:flex}
  .sheet-panel{border-radius:22px 22px 0 0}

  /* 回答方式：手机用入口按钮替代原 chips 行 */
  .modes{display:none}
  .mobile-mode-btn{
    display:flex;align-items:center;gap:8px;width:100%;min-height:44px;margin:0 0 8px;
    padding:0 12px;border:1px solid var(--line);border-radius:13px;
    background:rgba(255,253,248,.82);color:var(--brand);text-align:left;font-size:.84em;
  }
  .mobile-mode-btn::before{
    content:"回答方式";color:var(--faint);font-size:.86em;letter-spacing:.06em;font-weight:400;
  }
  .mobile-mode-btn::after{content:"›";color:var(--faint);font-size:.95em}
  #modeBtnText{flex:1;font-weight:700}

  /* 输入区：底部安全区与 44px 触控 */
  .composer-wrap{padding:0 10px calc(8px + env(safe-area-inset-bottom,0px))}
  .composer{padding:7px 8px;gap:6px;border-radius:18px}
  #micBtn{width:46px;height:46px;min-width:46px}
  .composer textarea{min-height:46px;padding:10px 4px}
  .send-btn{min-width:64px;height:46px;padding:0 12px}
  .composer-foot{margin-top:6px;padding:0 4px}
  .toast{bottom:calc(20px + env(safe-area-inset-bottom,0px))}
  /* 软键盘弹出时收起低频说明和模式入口，把高度留给输入框 */
  body.keyboard-open .mobile-mode-btn,
  body.keyboard-open .composer-foot{display:none}
  body.keyboard-open .composer-wrap{padding-bottom:8px}

  /* 聊天内容：欢迎页收紧、建议最多 3 个、实体 chips 横滑 */
  .chat-head{padding:10px 16px 6px}
  .chat-title{font-size:1.15em}
  .messages{padding:6px 14px 18px}
  .welcome{padding:18px 16px;border-radius:18px;margin:8px 0 18px}
  .welcome .eyebrow{font-size:.66em}
  .welcome h1{font-size:1.28em;line-height:1.4}
  .welcome p{font-size:.86em;margin-bottom:14px}
  .suggests{grid-template-columns:1fr;gap:8px}
  .suggest{min-height:48px;padding:11px 13px}
  .suggest:nth-child(n+4){display:none}
  .entity-strip{margin-top:14px;min-width:0;max-width:100%}
  .entity-label{color:var(--faint);font-size:.68em;letter-spacing:.08em;margin-bottom:6px}
  .entity-chips{
    display:flex;flex-wrap:nowrap;gap:7px;overflow-x:auto;padding:0 0 4px;
    max-width:100%;-webkit-overflow-scrolling:touch;scrollbar-width:none;
  }
  .entity-chips::-webkit-scrollbar{display:none}
  .entity-chip{
    flex:0 0 auto;min-height:40px;padding:7px 12px;border:1px solid var(--line);
    border-radius:999px;background:var(--card);font-size:.78em;white-space:nowrap;
  }
  .entity-chip span{margin-left:5px;color:var(--faint);font-size:.82em}
  .cites{grid-template-columns:1fr}
  .bubble .badge{display:inline-block;max-width:100%;margin:0 4px 4px 0;line-height:1.5;vertical-align:middle}
  /* 次要触控目标统一抬到 44px（反馈/归纳/小节/系列/小按钮/实体 chip） */
  .tool,.sum-btn,.section-btn,.series-tab,.small-btn,.entity-chip{min-height:44px}
}
@media (prefers-reduced-motion:reduce){
  *{animation:none!important;transition:none!important;scroll-behavior:auto!important}
}