:root{
  --bg:#f4f5fb;
  --bg2:#eef1f8;
  --panel:#ffffff;
  --panel2:#f8f9fd;
  --line:#d9dfea;
  --line-strong:#c7d0e2;
  --muted:#6b7280;
  --text:#1f2937;
  --sub:#374151;
  --purple:#5b54f1;
  --purple-2:#ecebff;
  --purple-3:#6f69ff;
  --green:#12945a;
  --green-bg:#e7f8ef;
  --red:#d44c5a;
  --red-bg:#fff0f2;
  --yellow:#b7791f;
  --yellow-bg:#fff7df;
  --blue:#4f46e5;
  --shadow:0 20px 48px rgba(86, 98, 131, .10);
}
*{box-sizing:border-box}
html{font-size:16px}
body{
  margin:0;
  background:linear-gradient(180deg,var(--bg) 0%, #f8f9fd 100%);
  color:var(--text);
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Noto Sans","PingFang SC","Microsoft YaHei",Arial,sans-serif;
  line-height:1.55;
}
.app{max-width:1280px;margin:0 auto;padding:30px 18px 42px}
header{
  display:flex;justify-content:space-between;gap:18px;align-items:flex-end;
  margin-bottom:18px;padding:0 2px 10px;
}
.brand h1{margin:0;font-size:42px;letter-spacing:-.045em;color:#111827}
.brand p{margin:8px 0 0;color:var(--muted);font-size:16px}
.controls{display:grid;grid-template-columns:1.5fr 1fr 1fr 1fr;gap:12px;margin-bottom:16px}
.controls input,.controls select{
  width:100%;background:#fff;border:1.5px solid var(--line);border-radius:18px;color:var(--text);
  padding:15px 16px;font-size:16px;outline:none;box-shadow:0 1px 0 rgba(255,255,255,.9) inset;
}
.controls input::placeholder{color:#9ca3af}
.controls input:focus,.controls select:focus{border-color:var(--purple);box-shadow:0 0 0 4px rgba(91,84,241,.08)}
.topline{display:flex;justify-content:space-between;gap:12px;align-items:center;margin:16px 0}
.modebar,.actions{display:flex;gap:10px;flex-wrap:wrap}
.btn{
  border:1.5px solid var(--line);background:#fff;color:var(--text);border-radius:18px;padding:12px 16px;
  font-weight:800;cursor:pointer;transition:.15s; font-size:15px; box-shadow:0 4px 12px rgba(86,98,131,.04);
}
.btn:hover{transform:translateY(-1px);border-color:#bfc8db}
.btn.active,.btn.primary{
  background:linear-gradient(180deg,var(--purple-3),var(--purple));
  color:#fff;border-color:transparent;box-shadow:0 10px 24px rgba(91,84,241,.25)
}
.btn.ghost{background:#fff}
.btn.warn{background:var(--yellow-bg);color:var(--yellow);border-color:#f0dd97}
.btn.small{padding:9px 12px;font-size:14px;border-radius:14px}
.layout{display:grid;grid-template-columns:300px 1fr;gap:18px}
.sidebar,.card{
  background:var(--panel);border:1.5px solid var(--line);border-radius:28px;box-shadow:var(--shadow)
}
.sidebar{padding:16px;max-height:76vh;overflow:auto;background:linear-gradient(180deg,#fff 0%, #fbfcff 100%)}
.statgrid{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin-bottom:14px}
.stat{
  background:var(--panel2);border:1px solid #e7ebf3;border-radius:18px;padding:12px 14px
}
.stat b{display:block;font-size:26px;color:#111827}
.stat span{color:var(--muted);font-size:13px}
.topiclist{display:flex;flex-direction:column;gap:10px}
.topicbtn{
  text-align:left;background:var(--panel2);border:1.5px solid #e5eaf4;color:var(--sub);border-radius:18px;padding:12px 13px;cursor:pointer
}
.topicbtn strong{display:block;color:#111827;font-size:14px;line-height:1.35}
.topicbtn span{font-size:12px;color:var(--muted)}
.topicbtn.active{border-color:rgba(91,84,241,.45);background:var(--purple-2);box-shadow:0 0 0 3px rgba(91,84,241,.07)}
.card{min-height:600px;padding:28px;background:linear-gradient(180deg,#fff 0%, #fcfcff 100%)}
.meta{display:flex;flex-wrap:wrap;gap:10px;margin-bottom:16px}
.pill{
  display:inline-flex;align-items:center;gap:6px;padding:7px 12px;border:1px solid #dde3ee;border-radius:999px;color:#4b5563;background:#f8f9fd;font-size:13px;font-weight:700
}
.pill.blue{border-color:#d7d5ff;color:#4338ca;background:#f0efff}
.pill.green{border-color:#caeedc;color:#157347;background:#effcf5}
.article-title{font-size:30px;line-height:1.22;margin:0 0 12px;letter-spacing:-.03em;color:#111827}
.context{
  border-left:4px solid var(--purple);padding:14px 16px;color:var(--sub);font-size:17px;margin:14px 0 22px;
  background:linear-gradient(90deg,rgba(91,84,241,.07),rgba(91,84,241,.02));border-radius:0 18px 18px 0
}
.context b{color:#111827}
.sentence-preview{font-size:26px;color:#111827;line-height:1.5;margin:14px 0 18px;font-weight:650}
.area{
  border:2px dashed #d9deeb;background:var(--panel2);border-radius:24px;min-height:128px;padding:16px;margin:12px 0;display:flex;flex-wrap:wrap;gap:10px;align-content:flex-start
}
.empty{color:#98a1b2;font-size:16px}
.chips{display:flex;flex-wrap:wrap;gap:10px;margin:16px 0 22px}
.chip{
  border:1.5px solid #dbe2ef;background:#fff;color:#1f2937;border-radius:999px;padding:12px 15px;cursor:pointer;font-size:18px;font-weight:600;transition:.12s;line-height:1.35
}
.chip:hover{border-color:#b9c3d9;transform:translateY(-1px);background:#fafbff}
.chip.used{display:none}
.chip.selected{background:var(--purple-2);border-color:#c8c4ff;color:#352fbf}
.feedback{min-height:28px;font-weight:800;font-size:18px}
.good{color:var(--green)}
.bad{color:var(--red)}
.recall-line{font-size:34px;line-height:2.05;margin:18px 0 26px;color:#111827;word-break:break-word}
.blank{
  display:inline-block;min-width:190px;max-width:320px;background:transparent;border:none;border-bottom:3px solid #cfd6e3;
  color:#1f2937;text-align:center;font:inherit;font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;outline:none;padding:0 6px 6px;margin:0 2px
}
.blank::placeholder{color:#aab1c1}
.blank:focus{border-color:var(--purple)}
.blank.correct{border-color:var(--green);color:var(--green)}
.blank.incorrect{border-color:var(--red);color:var(--red)}
details{margin-top:16px;color:var(--muted);background:#fafbff;border:1px solid #ebeff6;border-radius:18px;padding:12px 14px}
summary{cursor:pointer;color:#374151;font-size:18px;font-weight:700}
.source a{color:#4f46e5;text-decoration:none;overflow-wrap:anywhere}
.source a:hover{text-decoration:underline}
.footer-actions{display:flex;justify-content:space-between;gap:12px;align-items:center;border-top:1px solid #ebeff5;padding-top:18px;margin-top:18px}
.progress{color:var(--muted);font-size:14px;font-weight:600}
.kbd{font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;background:#f1f3f9;border:1px solid #d6deea;border-bottom-width:2px;border-radius:8px;padding:3px 6px;color:#111827;font-size:12px}
.mobile-note{display:none}
.review{background:#f9faff;border:1px solid #e5eaf3;border-radius:20px;padding:16px;margin-top:14px}
.hidden{display:none!important}
.hint-banner{
  margin:14px 0 0;padding:12px 14px;border-radius:18px;background:#f7f8fc;border:1px dashed #d7deeb;color:#5b6475;font-size:16px
}
.hint-banner b{color:#374151}

@media(max-width:980px){
  .controls{grid-template-columns:1fr 1fr}
  .layout{grid-template-columns:1fr}
  .sidebar{max-height:280px}
}
@media(max-width:760px){
  header{display:block}
  .controls{grid-template-columns:1fr}
  .topline{display:block}
  .modebar{margin-bottom:10px}
  .card{padding:18px}
  .article-title{font-size:24px}
  .recall-line{font-size:26px;line-height:1.9}
  .sentence-preview{font-size:22px}
  .chip{font-size:16px}
  .mobile-note{display:block;color:var(--muted);font-size:13px;margin-bottom:8px}
  .footer-actions{display:block}
  .footer-actions .actions{margin-bottom:12px}
}

header .actions{max-width:640px;justify-content:flex-end}
@media(max-width:760px){
  header .actions{max-width:none;justify-content:flex-start;margin-top:14px}
}

.footer-actions{
  display:grid;
  grid-template-columns:auto 1fr auto;
  align-items:center;
}
.footer-mid{
  justify-content:center;
}
@media(max-width:760px){
  .footer-actions{
    display:block;
  }
  .footer-mid{
    justify-content:flex-start;
    margin:10px 0;
  }
}

.reconstruct-head{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:16px;
  flex-wrap:wrap;
  margin-top:10px;
}
.reconstruct-head .sentence-preview{
  margin:0;
}
.difficultybar{
  display:flex;
  align-items:center;
  gap:8px;
  background:#f7f8fc;
  border:1px solid #e2e7f1;
  border-radius:999px;
  padding:6px;
}
.difficulty-label{
  color:#6b7280;
  font-size:13px;
  font-weight:800;
  padding:0 4px 0 8px;
}
.mini-toggle{
  border:0;
  background:transparent;
  color:#4b5563;
  border-radius:999px;
  padding:8px 12px;
  font-weight:900;
  cursor:pointer;
}
.mini-toggle.active{
  background:linear-gradient(180deg,var(--purple-3),var(--purple));
  color:#fff;
  box-shadow:0 8px 18px rgba(91,84,241,.20);
}
@media(max-width:760px){
  .reconstruct-head{
    align-items:flex-start;
  }
  .difficultybar{
    width:100%;
    justify-content:space-between;
  }
}