:root{
  --bg:#eef2f6; --card:#ffffff; --ink:#2b3346; --ink2:#6a7388; --ink3:#9aa3b5;
  --line:rgba(30,45,70,.10); --accent:#6d6ae0; --accent-soft:#ecebff;
  --pink:#d96fa6; --green:#3aa675; --amber:#d9922b; --red:#d95c5c;
  --shadow:0 1px 2px rgba(30,45,70,.05),0 4px 16px rgba(30,45,70,.06);
}
*{box-sizing:border-box}
html,body{margin:0;height:100%}
body{
  background:var(--bg); color:var(--ink);
  font:15px/1.65 -apple-system,"PingFang SC","Microsoft YaHei",Segoe UI,Roboto,sans-serif;
}
button,input,textarea,select{font:inherit;color:inherit}
button{cursor:pointer}

/* topbar */
.topbar{display:flex;align-items:center;gap:20px;padding:12px 20px;background:var(--card);
  border-bottom:1px solid var(--line);position:sticky;top:0;z-index:20}
.brand{display:flex;align-items:center;gap:10px}
.logo{width:38px;height:38px;border-radius:11px;background:linear-gradient(135deg,#6d6ae0,#8f7ff0);
  color:#fff;display:grid;place-items:center;font-weight:700;font-size:14px;letter-spacing:.5px}
.brand-txt{display:flex;flex-direction:column;line-height:1.3}
.brand-txt small{color:var(--ink3);font-size:12px}
.stats{margin-left:auto;display:flex;gap:18px;color:var(--ink2);font-size:13px}
.stats b{color:var(--ink);font-size:15px;margin-right:4px}
.user-area{display:flex;align-items:center;gap:10px;font-size:13px}
.user-area .who{color:var(--ink2);max-width:180px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.btn{border:1px solid var(--line);background:var(--card);border-radius:9px;padding:7px 14px;color:var(--ink)}
.btn:hover{border-color:#cfd6e2}
.btn.primary{background:var(--accent);border-color:var(--accent);color:#fff}
.btn.primary:hover{filter:brightness(1.05)}
.btn.sm{padding:4px 10px;font-size:13px;border-radius:7px}
.btn.ghost{background:transparent;border-color:transparent;color:var(--ink2)}

/* layout */
.layout{display:grid;grid-template-columns:284px minmax(0,1fr);gap:18px;padding:18px;
  align-items:start;min-height:calc(100vh - 63px)}
.sidebar{background:var(--card);border:1px solid var(--line);border-radius:14px;box-shadow:var(--shadow);
  display:flex;flex-direction:column;max-height:calc(100vh - 100px);position:sticky;top:81px}
.side-head{padding:12px;border-bottom:1px solid var(--line)}
#search{width:100%;border:1px solid var(--line);border-radius:9px;padding:8px 11px;background:#f7f9fc;outline:none}
#search:focus{border-color:var(--accent);background:#fff}
.filters{display:flex;gap:6px;margin-top:9px}
.filters button{flex:1;border:1px solid var(--line);background:#f7f9fc;border-radius:8px;padding:5px 0;font-size:12.5px;color:var(--ink2)}
.filters button.on{background:var(--accent-soft);border-color:#c9c6ff;color:#4a47b8;font-weight:600}
.side-progress{display:flex;align-items:center;gap:9px;margin-top:10px;font-size:12px;color:var(--ink2)}
.bar{flex:1;height:6px;border-radius:4px;background:#eaedf3;overflow:hidden}
.bar i{display:block;height:100%;width:0;background:linear-gradient(90deg,#6d6ae0,#8f7ff0);transition:width .3s}
.legend{display:flex;gap:12px;margin-top:9px;font-size:11.5px;color:var(--ink3);flex-wrap:wrap}
.legend span{display:inline-flex;align-items:center;gap:4px}
.lesson-list{list-style:none;margin:0;padding:6px;overflow:auto;flex:1}
.lesson-list li{display:flex;align-items:center;gap:8px;padding:7px 9px;border-radius:9px;cursor:pointer}
.lesson-list li:hover{background:#f5f7fb}
.lesson-list li.on{background:var(--accent-soft)}
.lesson-list li.on .no{color:#4a47b8}
.no{width:30px;text-align:right;color:var(--ink3);font-size:12.5px;flex:none;font-variant-numeric:tabular-nums}
.tt{flex:1;min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;font-size:13.5px}
.tt em{font-style:normal;color:var(--ink3);font-size:12px;margin-left:5px}
.dots{display:flex;gap:3px;flex:none}
.dot{width:7px;height:7px;border-radius:50%;background:#dfe3ea}
.dot.s{background:var(--accent)} .dot.p{background:var(--green)} .dot.r{background:var(--amber)}
.dot.review-due{box-shadow:0 0 0 3px rgba(217,146,43,.18)}

/* main */
.main{min-width:0}
.lesson-head{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:14px 18px;
  box-shadow:var(--shadow);margin-bottom:14px;display:flex;align-items:flex-start;gap:14px;flex-wrap:wrap}
.lesson-head h1{margin:0;font-size:20px}
.lesson-head .zh{color:var(--ink2);font-size:14px;margin-top:2px}
.lesson-head .spacer{flex:1}
.lesson-head .acts{display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.tabs{display:flex;gap:6px;margin-bottom:14px}
.tabs button{border:1px solid var(--line);background:var(--card);border-radius:10px;padding:8px 18px;color:var(--ink2)}
.tabs button.on{background:var(--accent);border-color:var(--accent);color:#fff;font-weight:600}
.view{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:20px;box-shadow:var(--shadow);min-height:340px}

/* content bits */
.sec{margin-bottom:22px}
.sec h3{margin:0 0 10px;font-size:15px;display:flex;align-items:center;gap:8px}
.sec h3 small{color:var(--ink3);font-weight:400;font-size:12.5px}
.sent{padding:9px 12px;border-radius:10px;transition:background .15s}
.sent+.sent{margin-top:2px}
.sent:hover{background:#f7f9fc}
.sent .en{font-size:16px;letter-spacing:.1px}
.sent .zh{color:var(--ink2);font-size:13.5px;margin-top:2px}
.sent.masked .en,.sent.masked .zh{filter:blur(5px);cursor:pointer;user-select:none}
.sent .sp{color:var(--ink3);font-size:12px;margin-left:6px}
.words{display:flex;flex-wrap:wrap;gap:7px}
.word{background:#f7f9fc;border:1px solid var(--line);border-radius:8px;padding:5px 10px;font-size:13px}
.word b{font-weight:600} .word span{color:var(--ink2)}
.prose{white-space:pre-wrap;color:var(--ink);font-size:14.5px;line-height:1.85}
.muted{color:var(--ink3);font-size:13px}
.empty{padding:36px 0;text-align:center;color:var(--ink3)}

/* exercise */
.ex{border:1px solid var(--line);border-radius:12px;padding:14px 16px;margin-bottom:12px;background:#fcfdff}
.ex .qhead{display:flex;align-items:center;gap:8px;margin-bottom:8px;font-size:12px;color:var(--ink3)}
.tag{border-radius:6px;padding:2px 7px;font-size:11.5px;background:#eef1f7;color:var(--ink2)}
.tag.fill{background:#ecebff;color:#4a47b8} .tag.choice{background:#e6f4ee;color:#2c7a5b}
.tag.write{background:#fdeef5;color:#a94b7c} .tag.custom{background:#fff4e3;color:#a56a1b}
.ex .q{font-size:16px;margin:0 0 10px;line-height:1.7}
.ex .q .gap{display:inline-block;min-width:78px;border-bottom:2px solid var(--accent);text-align:center;color:transparent}
.opt{display:block;border:1px solid var(--line);border-radius:9px;padding:8px 12px;margin-bottom:6px;background:#fff;cursor:pointer}
.opt:hover{border-color:#c9c6ff}
.opt.pick{border-color:var(--accent);background:var(--accent-soft)}
.opt.right{border-color:var(--green);background:#e9f7f0}
.opt.wrong{border-color:var(--red);background:#fdeeee}
textarea.ans,input.ans{width:100%;border:1px solid var(--line);border-radius:9px;padding:9px 12px;background:#fff;outline:none}
textarea.ans{min-height:64px;resize:vertical}
input.ans:focus,textarea.ans:focus{border-color:var(--accent)}
.fb{margin-top:9px;font-size:13.5px;border-radius:9px;padding:8px 11px}
.fb.ok{background:#e9f7f0;color:#23694c}
.fb.no{background:#fdeeee;color:#9c3b3b}
.fb .key{color:var(--ink2)}
.ex .tools{display:flex;gap:8px;margin-top:10px;flex-wrap:wrap;align-items:center}
.score{margin-left:auto;font-size:13px;color:var(--ink2)}
.addbox{border:1px dashed #c7cede;border-radius:12px;padding:14px;margin-top:6px;background:#fbfcfe}
.addbox h4{margin:0 0 10px;font-size:14px}
.grid2{display:grid;grid-template-columns:1fr 1fr;gap:10px}
label.fld{display:flex;flex-direction:column;gap:4px;font-size:12.5px;color:var(--ink2)}
label.fld input,label.fld textarea,label.fld select{border:1px solid var(--line);border-radius:8px;padding:7px 10px;background:#fff}

/* review */
.rv-card{border:1px solid var(--line);border-radius:12px;padding:14px 16px;margin-bottom:12px}
.rv-card.due{border-color:#f0d9b5;background:#fffaf2}
.rv-head{display:flex;align-items:center;gap:10px;flex-wrap:wrap;margin-bottom:8px}
.rv-head b{font-size:15px}
.rv-steps{display:flex;gap:10px;flex-wrap:wrap;margin-bottom:10px}
.rv-step{display:inline-flex;align-items:center;gap:7px;border:1px solid var(--line);background:#fff;
  border-radius:10px;padding:9px 14px;font-size:13.5px;color:var(--ink)}
.rv-step:hover{border-color:#c9c6ff;background:var(--accent-soft)}
.rv-step .tick{width:18px;height:18px;border-radius:50%;background:#eef1f7;color:var(--ink3);
  display:grid;place-items:center;font-size:11px}
.rv-step.done{border-color:#bfe3d0;background:#eefaf3;color:#23694c}
.rv-step.done .tick{background:var(--green);color:#fff}
.pill{border-radius:20px;padding:2px 10px;font-size:12px;background:#eef1f7;color:var(--ink2)}
.pill.due{background:#fdeedd;color:#a56a1b}
.pill.ok{background:#e9f7f0;color:#23694c}

/* ---- 音频朗读条 ---- */
.audio-bar{display:flex;align-items:center;gap:12px;background:linear-gradient(135deg,#6d6ae0,#8f7ff0);
  color:#fff;border-radius:14px;padding:12px 16px;margin-bottom:14px;flex-wrap:wrap;box-shadow:var(--shadow)}
.audio-bar .ab-play{width:44px;height:44px;border:none;border-radius:50%;background:#fff;color:#6d6ae0;
  font-size:17px;display:grid;place-items:center;flex:none;box-shadow:0 4px 12px rgba(40,30,90,.25)}
.audio-bar .ab-play:active{transform:scale(.95)}
.audio-bar .ab-prog{flex:1;min-width:150px;height:9px;border-radius:6px;background:rgba(255,255,255,.35);
  cursor:pointer;position:relative;overflow:hidden}
.audio-bar .ab-prog i{position:absolute;left:0;top:0;height:100%;width:0;background:#fff;border-radius:6px}
.audio-bar .ab-time{font-size:12.5px;font-variant-numeric:tabular-nums;min-width:92px;text-align:center}
.audio-bar .ab-rate{display:flex;align-items:center;gap:6px;font-size:12.5px}
.audio-bar .ab-rate select{margin:0;border:none;border-radius:7px;padding:4px 6px;color:var(--ink);background:#fff}
.audio-bar .ab-loop{border:1px solid rgba(255,255,255,.6);background:transparent;color:#fff;border-radius:9px;
  padding:6px 12px;font-size:12.5px}
.audio-bar .ab-loop.on{background:#fff;color:#6d6ae0;font-weight:600}
.audio-note{font-size:12.5px;color:var(--ink3);margin:-4px 0 16px}

/* ---- 同步高亮 ---- */
.sent.active{background:var(--accent-soft);box-shadow:inset 3px 0 0 var(--accent);border-radius:10px}
.sent.active .en{font-weight:600}
.para.cur{background:rgba(109,106,224,.05);border-radius:12px}
.sent-play{float:right;margin:0 0 0 10px;border:1px solid var(--line);background:#fff;border-radius:8px;
  width:30px;height:30px;display:none;place-items:center;color:var(--accent);font-size:12px;line-height:1}
.sent:hover .sent-play{display:grid}
.sent.playing .sent-play{display:grid;background:var(--accent);color:#fff;border-color:var(--accent)}

/* ---- 练习反馈框（修复宽度/溢出） ---- */
.fb-slot{flex:0 0 100%;width:100%;min-width:0;margin-top:9px}
.fb{font-size:13.5px;border-radius:9px;padding:9px 11px;overflow-wrap:anywhere;word-break:break-word;max-width:100%;width:100%}
.fb.ok{background:#e9f7f0;color:#23694c}
.fb.no{background:#fdeeee;color:#9c3b3b}
.fb .key{color:var(--ink2)}
.ex .tools{align-items:flex-start}

/* ---- 三色笔记 ---- */
.notes-legend{display:flex;gap:14px;flex-wrap:wrap;font-size:12.5px;margin-bottom:8px}
.notes-legend span{display:inline-flex;align-items:center;gap:6px}
.notes-legend i{width:11px;height:11px;border-radius:3px;display:inline-block}
.np{border:1px solid var(--line);border-left-width:4px;border-radius:10px;padding:10px 14px;margin-bottom:10px;background:#fff}
.np.key{border-left-color:var(--accent)}
.np.hard{border-left-color:var(--amber)}
.np.err{border-left-color:var(--red)}
.np-head{display:flex;align-items:center;gap:10px;margin-bottom:5px}
.np-cat{cursor:pointer;font-size:12px;font-weight:600;padding:2px 10px;border-radius:20px;user-select:none}
.np.key .np-cat{background:var(--accent-soft);color:#4a47b8}
.np.hard .np-cat{background:#fbf0dd;color:#a56a1b}
.np.err .np-cat{background:#fdeeee;color:#9c3b3b}
.np-must{margin-left:auto;border:1px solid var(--line);background:#fff;border-radius:20px;padding:3px 11px;
  font-size:12px;color:var(--ink3)}
.np-must.on{background:linear-gradient(135deg,#f6c453,#f0a93b);border-color:#f0a93b;color:#5a3d05;font-weight:600}
.np-body{font-size:14px;line-height:1.8;color:var(--ink);white-space:pre-wrap}
.np-body b{color:var(--ink)}
.must-list{display:flex;flex-direction:column;gap:6px;margin-top:8px}
.must-list .mi{border:1px solid #f0d9b5;background:#fffaf2;border-radius:9px;padding:7px 12px;font-size:13px;color:var(--ink)}

/* modal */
.modal{position:fixed;inset:0;background:rgba(28,36,54,.42);display:grid;place-items:center;z-index:60;padding:20px}
.modal-card{background:var(--card);border-radius:16px;padding:22px;width:min(420px,100%);box-shadow:0 20px 60px rgba(20,30,50,.24);position:relative}
.modal-tabs{display:flex;gap:6px;margin-bottom:16px}
.modal-tabs button{flex:1;border:1px solid var(--line);background:#f7f9fc;border-radius:9px;padding:7px 0;font-size:13px;color:var(--ink2)}
.modal-tabs button.on{background:var(--accent);border-color:var(--accent);color:#fff;font-weight:600}
.auth-form{display:flex;flex-direction:column;gap:12px}
.auth-form label{display:flex;flex-direction:column;gap:5px;font-size:12.5px;color:var(--ink2)}
.auth-form input{border:1px solid var(--line);border-radius:9px;padding:9px 12px;background:#fbfcfe;outline:none}
.code-row{display:flex;gap:8px}
.code-row input{flex:1}
.code-row button{border:1px solid var(--line);background:#f2f5fa;border-radius:9px;padding:0 12px;font-size:12.5px;white-space:nowrap}
.row{display:flex;align-items:center;gap:12px}
.row .primary{flex:1}
.link{border:none;background:none;color:var(--accent);font-size:12.5px;padding:0}
.hint{min-height:18px;font-size:12.5px;color:var(--red)}
.hint.ok{color:var(--green)}
.modal-tip{margin:14px 0 0;font-size:12px;color:var(--ink3);line-height:1.6}
.close{position:absolute;top:12px;right:14px;border:none;background:none;color:var(--ink3);font-size:13px}

.toast{position:fixed;left:50%;bottom:34px;transform:translateX(-50%);background:#2b3346;color:#fff;
  padding:10px 18px;border-radius:10px;font-size:13.5px;z-index:80;box-shadow:0 8px 24px rgba(20,30,50,.24)}

@media (max-width:900px){
  .layout{grid-template-columns:1fr}
  .sidebar{position:static;max-height:380px}
  .stats{display:none}
}