:root{
  --bg:#FFF8EF; --card:#FFFFFF; --ink:#2B2B3A; --soft:#6B6B7B;
  --pri:#4F7BE0; --pri-d:#3A63C4; --acc:#FF8A5C; --good:#2FA97C; --bad:#E05B5B;
  --warn:#E8A33D; --line:#EFE3D3; --shadow:0 6px 24px rgba(60,50,30,.08);
  --purple:#7B61C9; --rbx:#E2231A;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  font-family:"Noto Sans TC","PingFang HK","Microsoft JhengHei",sans-serif;
  background:var(--bg); color:var(--ink); line-height:1.75; font-size:17px;
  -webkit-tap-highlight-color:transparent;
}
.hidden{display:none!important}
button{font-family:inherit}
#topbar{
  position:sticky; top:0; z-index:50; display:flex; align-items:center; gap:14px;
  padding:10px 16px; background:rgba(255,248,239,.92); backdrop-filter:blur(8px);
  border-bottom:1px solid var(--line);
}
.brand{display:flex; align-items:center; gap:10px; cursor:pointer; font-weight:900}
.brand-name{font-family:"Baloo 2","Noto Sans TC",sans-serif; font-size:1.25rem; color:var(--pri-d)}
.brand-name small{color:var(--acc); font-size:.85rem; margin-left:2px}
#topnav{display:flex; gap:4px; margin-left:auto; flex-wrap:wrap}
#topnav a{
  text-decoration:none; color:var(--soft); font-weight:700; font-size:.95rem;
  padding:8px 12px; border-radius:999px; min-height:40px; display:inline-flex; align-items:center;
}
#topnav a.active,#topnav a:hover{background:#fff; color:var(--pri-d); box-shadow:var(--shadow)}
.top-actions{display:flex; gap:8px}
.chip{
  border:1.5px solid var(--line); background:#fff; border-radius:999px;
  padding:8px 14px; font-weight:700; cursor:pointer; color:var(--pri-d); min-height:40px;
}
.chip.off{color:#bbb}
.chip.on{background:var(--pri); color:#fff; border-color:var(--pri)}
#teacherBar{
  display:flex; gap:14px; align-items:flex-start;
  margin:14px auto 0; max-width:960px; padding:12px 18px;
  background:linear-gradient(135deg,#EEF3FF,#FFF3EA);
  border:1.5px solid var(--line); border-radius:20px; box-shadow:var(--shadow);
  position:relative; z-index:40; width:calc(100% - 24px);
}
.teacher-say{flex:1; min-width:0}
.teacher-name{font-weight:900; color:var(--pri-d); font-size:.9rem}
#teacherText{min-height:2.2em; font-size:1.02rem}
.teacher-ctrl{display:flex; gap:8px; margin-top:6px; flex-wrap:wrap}
.owl{width:44px; height:44px; flex:none}
.owl.big{width:74px; height:74px}
.owl svg{width:100%; height:100%; display:block; overflow:visible}
#app{max-width:960px; margin:0 auto; padding:20px 14px 80px}
.card{
  background:var(--card); border:1.5px solid var(--line); border-radius:20px;
  padding:20px; box-shadow:var(--shadow); margin-bottom:16px;
}
.card h2,.card h3{margin-top:0}
.grid{display:grid; gap:14px}
.grid.c2{grid-template-columns:repeat(auto-fill,minmax(280px,1fr))}
.muted{color:var(--soft)}
.tiny{font-size:.85rem}
.center{text-align:center}
hr.soft{border:none; border-top:1.5px dashed var(--line); margin:16px 0}
.btn{
  display:inline-flex; align-items:center; justify-content:center; gap:8px;
  background:var(--pri); color:#fff; border:none; border-radius:16px;
  padding:14px 22px; font-size:1.05rem; font-weight:700; cursor:pointer;
  min-height:52px; box-shadow:0 4px 0 var(--pri-d); transition:transform .08s, box-shadow .08s;
  text-decoration:none;
}
.btn:active{transform:translateY(3px); box-shadow:0 1px 0 var(--pri-d)}
.btn.ghost{background:#fff; color:var(--pri-d); border:2px solid var(--pri); box-shadow:none}
.btn.acc{background:var(--acc); box-shadow:0 4px 0 #D96C3E}
.btn.acc:active{box-shadow:0 1px 0 #D96C3E}
.btn.good{background:var(--good); box-shadow:0 4px 0 #1F7A59}
.btn.good:active{box-shadow:0 1px 0 #1F7A59}
.btn.small{padding:8px 14px; min-height:40px; font-size:.9rem; border-radius:12px}
.btn:disabled{opacity:.45; cursor:not-allowed; box-shadow:none}
.btn.rbx{background:var(--rbx); box-shadow:0 4px 0 #8f1510; font-family:"Baloo 2",sans-serif}
.btn.rbx:active{box-shadow:0 1px 0 #8f1510}
footer{
  text-align:center; color:var(--soft); font-size:.85rem; padding:24px 12px 40px;
  display:flex; flex-direction:column; gap:4px;
}
@media(max-width:640px){
  #topnav a{padding:8px 8px; font-size:.85rem}
  .brand-name{font-size:1.05rem}
  body{font-size:16px}
}

/* ===== TTS 字幕同步條：Lumi 老師讀邊句、字幕顯示邊句（聽唔到聲都睇到講解） ===== */
#ttsCap{
  position:fixed; left:50%; transform:translateX(-50%) translateY(10px);
  bottom:max(14px, env(safe-area-inset-bottom));
  z-index:2600; max-width:min(92vw,680px);
  background:rgba(22,18,38,.93); color:#fff;
  padding:13px 22px; border-radius:18px;
  font-size:1.18rem; line-height:1.75; font-weight:500; text-align:center;
  box-shadow:0 10px 34px rgba(0,0,0,.4);
  border:1px solid rgba(255,255,255,.12);
  opacity:0; pointer-events:none;
  transition:opacity .28s ease, transform .28s ease;
}
#ttsCap.show{ opacity:1; transform:translateX(-50%) translateY(0); }
@media(max-width:640px){ #ttsCap{ font-size:1.06rem; padding:11px 16px; } }