:root{
  --bg:#f4f6fb; --panel:#fff; --panel-2:#fafbfe; --border:#e4e9f2;
  --text:#1c2434; --dim:#6b7688;
  --primary:#4f6ef7; --primary-soft:#edf0ff;
  --ok:#12a150; --ok-soft:#e6f7ee;
  --bad:#e5484d; --bad-soft:#fdecec;
  --warn:#c47b00; --warn-soft:#fff4e0;
  --radius:14px;
  --shadow:0 1px 3px rgba(20,30,60,.05), 0 8px 24px -14px rgba(20,30,60,.25);
}
@media (prefers-color-scheme: dark){
  :root{
    --bg:#0f1319; --panel:#171c25; --panel-2:#1c222d; --border:#28303d;
    --text:#e6eaf2; --dim:#8b96a8;
    --primary:#6b85ff; --primary-soft:#1e2740;
    --ok:#3ecf7a; --ok-soft:#12301f;
    --bad:#ff6b6f; --bad-soft:#33161a;
    --warn:#e0a952; --warn-soft:#33280f;
    --shadow:0 1px 3px rgba(0,0,0,.3), 0 8px 24px -14px rgba(0,0,0,.8);
  }
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  background:var(--bg);color:var(--text);line-height:1.65;
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;
  -webkit-font-smoothing:antialiased;
}
button,textarea{font-family:inherit}

.topbar{position:sticky;top:0;z-index:50;display:flex;align-items:center;gap:18px;
  height:60px;padding:0 24px;background:var(--panel);border-bottom:1px solid var(--border)}
.brand{font-size:16px;font-weight:700;white-space:nowrap}
.nav{display:flex;gap:4px;flex:1}
.nav button{border:none;background:transparent;cursor:pointer;padding:8px 14px;
  border-radius:9px;font-size:14px;font-weight:500;color:var(--dim);transition:.15s}
.nav button:hover{background:var(--panel-2);color:var(--text)}
.nav button.active{background:var(--primary-soft);color:var(--primary);font-weight:600}
.mini-stat{font-size:13px;color:var(--dim);white-space:nowrap}
.mini-stat b{color:var(--text)}

.container{max-width:1140px;margin:0 auto;padding:24px}
.dim{color:var(--dim)}
.btn{border:none;border-radius:10px;padding:9px 16px;font-size:14px;font-weight:600;
  cursor:pointer;transition:.15s;white-space:nowrap}
.btn:disabled{opacity:.4;cursor:not-allowed}
.btn.primary{background:var(--primary);color:#fff}
.btn.primary:hover:not(:disabled){filter:brightness(1.08)}
.btn.ghost{background:var(--panel);color:var(--text);border:1px solid var(--border)}
.btn.ghost:hover:not(:disabled){border-color:var(--primary);color:var(--primary)}
.btn.lg{padding:12px 24px;font-size:15px}
.btn.sm{padding:6px 12px;font-size:13px}

.hero{display:flex;justify-content:space-between;align-items:center;gap:20px;flex-wrap:wrap;
  background:linear-gradient(135deg,#4f6ef7 0%,#7b5cff 100%);color:#fff;
  border-radius:18px;padding:28px;margin-bottom:20px;box-shadow:var(--shadow)}
.hero h1{margin:0 0 6px;font-size:24px}
.hero p{margin:0;font-size:14px;color:rgba(255,255,255,.82)}
.hero-actions{display:flex;gap:10px;flex-wrap:wrap}
.hero .btn.primary{background:#fff;color:#4f6ef7}
.hero .btn.ghost{background:rgba(255,255,255,.16);color:#fff;border-color:rgba(255,255,255,.4)}
.hero .btn.ghost:hover{background:rgba(255,255,255,.26);color:#fff}

.stat-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));gap:14px;margin-bottom:20px}
.stat{background:var(--panel);border:1px solid var(--border);border-radius:var(--radius);padding:16px 18px}
.stat .num{font-size:26px;font-weight:700;line-height:1.2}
.stat .num.ok{color:var(--ok)} .stat .num.bad{color:var(--bad)}
.stat .label{font-size:13px;color:var(--dim);margin-top:2px}

.panel{background:var(--panel);border:1px solid var(--border);border-radius:var(--radius);
  padding:20px;box-shadow:var(--shadow)}
.panel h2{margin:0 0 16px;font-size:16px}
.cat-row{display:grid;grid-template-columns:110px 1fr 60px;align-items:center;gap:14px;
  padding:9px 8px;border-radius:10px;cursor:pointer;transition:.15s}
.cat-row:hover{background:var(--panel-2)}
.cat-name{font-size:14px;font-weight:500}
.bar{height:7px;background:var(--border);border-radius:999px;overflow:hidden}
.bar-fill{height:100%;background:var(--primary);border-radius:999px;transition:width .4s}
.cat-num{font-size:13px;color:var(--dim);text-align:right;font-variant-numeric:tabular-nums}
.footer-actions{margin-top:24px;display:flex;gap:10px;justify-content:center;flex-wrap:wrap}

.filters{display:flex;gap:10px;flex-wrap:wrap;align-items:center;margin-bottom:18px}
select{font-family:inherit;font-size:14px;padding:8px 12px;border-radius:10px;
  border:1px solid var(--border);background:var(--panel);color:var(--text);cursor:pointer;outline:none}
select:focus{border-color:var(--primary)}

.practice-layout{display:grid;grid-template-columns:minmax(0,1fr) 236px;gap:20px;align-items:start}
.question-panel{background:var(--panel);border:1px solid var(--border);border-radius:var(--radius);
  padding:24px;box-shadow:var(--shadow)}
.q-head{display:flex;gap:8px;align-items:center;flex-wrap:wrap;margin-bottom:16px}
.tag{font-size:12px;font-weight:600;padding:3px 10px;border-radius:999px}
.tag.cat{background:var(--primary-soft);color:var(--primary)}
.tag.easy{background:var(--ok-soft);color:var(--ok)}
.tag.medium{background:var(--warn-soft);color:var(--warn)}
.tag.hard{background:var(--bad-soft);color:var(--bad)}
.tag.type{background:var(--panel-2);color:var(--dim);border:1px solid var(--border)}
.q-counter{margin-left:auto;font-size:13px;color:var(--dim);font-variant-numeric:tabular-nums}
.stem{font-size:17px;font-weight:600;line-height:1.7;margin:0 0 18px}

.option{display:flex;gap:12px;align-items:flex-start;padding:13px 16px;margin-bottom:10px;
  border:1.5px solid var(--border);border-radius:12px;background:var(--panel-2);
  cursor:pointer;transition:.15s;user-select:none}
.option:hover{border-color:var(--primary);background:var(--primary-soft)}
.option.selected{border-color:var(--primary);background:var(--primary-soft)}
.option.correct{border-color:var(--ok);background:var(--ok-soft)}
.option.wrong{border-color:var(--bad);background:var(--bad-soft)}
.opt-letter{flex:0 0 26px;height:26px;border-radius:8px;display:grid;place-items:center;
  background:var(--panel);border:1px solid var(--border);font-size:13px;font-weight:700;color:var(--dim)}
.option.selected .opt-letter{background:var(--primary);border-color:var(--primary);color:#fff}
.option.correct .opt-letter{background:var(--ok);border-color:var(--ok);color:#fff}
.option.wrong .opt-letter{background:var(--bad);border-color:var(--bad);color:#fff}
.opt-text{flex:1;font-size:15px;padding-top:1px}

.result{margin-top:18px;border-radius:12px;padding:16px 18px;font-size:14px}
.result.ok{background:var(--ok-soft);border:1px solid var(--ok)}
.result.bad{background:var(--bad-soft);border:1px solid var(--bad)}
.result-title{font-weight:700;margin-bottom:8px}
.result.ok .result-title{color:var(--ok)}
.result.bad .result-title{color:var(--bad)}
.answer-line{margin-bottom:8px}
.analysis{opacity:.9;line-height:1.75}

.q-actions{display:flex;gap:10px;align-items:center;margin-top:22px;flex-wrap:wrap}
.spacer{flex:1}

.card-panel{position:sticky;top:80px;background:var(--panel);border:1px solid var(--border);
  border-radius:var(--radius);padding:16px;box-shadow:var(--shadow)}
.card-panel h3{margin:0 0 4px;font-size:14px}
.card-summary{font-size:12px;color:var(--dim);margin-bottom:12px}
.card-summary b{color:var(--text)}
.card-summary .ok{color:var(--ok)}
.card-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(36px,1fr));gap:7px;
  max-height:60vh;overflow-y:auto}
.card-item{aspect-ratio:1;border-radius:9px;cursor:pointer;border:1.5px solid var(--border);
  background:var(--panel-2);color:var(--dim);font-size:13px;font-weight:600;
  display:grid;place-items:center;transition:.15s;padding:0}
.card-item:hover{border-color:var(--primary)}
.card-item.ok{background:var(--ok-soft);border-color:transparent;color:var(--ok)}
.card-item.bad{background:var(--bad-soft);border-color:transparent;color:var(--bad)}
.card-item.current{outline:2px solid var(--primary);outline-offset:1px}

.empty{background:var(--panel);border:1px solid var(--border);border-radius:var(--radius);
  padding:60px 24px;text-align:center;box-shadow:var(--shadow)}
.empty-icon{font-size:40px;margin-bottom:8px}
.empty h2{margin:0 0 6px;font-size:18px}
.empty p{margin:0 0 20px;font-size:14px}

.toast{position:fixed;left:50%;bottom:40px;z-index:200;transform:translate(-50%,16px);
  background:var(--text);color:var(--panel);padding:10px 22px;border-radius:999px;
  font-size:14px;font-weight:500;opacity:0;transition:.3s;pointer-events:none}
.toast.show{opacity:1;transform:translate(-50%,0)}

.modal{position:fixed;inset:0;z-index:150;background:rgba(10,15,30,.55);
  display:none;align-items:center;justify-content:center;padding:24px}
.modal.show{display:flex}
.modal-box{background:var(--panel);border-radius:16px;padding:24px;width:100%;max-width:680px;
  max-height:86vh;overflow-y:auto;box-shadow:0 20px 60px -20px rgba(0,0,0,.5)}
.modal-box h2{margin:0 0 6px;font-size:18px}
.modal-box p.hint{margin:0 0 14px;font-size:13px;color:var(--dim)}
.modal-box textarea{width:100%;height:260px;resize:vertical;
  font-family:ui-monospace,Menlo,Consolas,monospace;font-size:12.5px;line-height:1.55;
  padding:12px;border-radius:10px;border:1px solid var(--border);
  background:var(--panel-2);color:var(--text);outline:none}
.modal-box textarea:focus{border-color:var(--primary)}
.modal-actions{display:flex;gap:10px;justify-content:flex-end;margin-top:16px;flex-wrap:wrap}
.import-msg{font-size:13px;margin-top:10px}
.import-msg.ok{color:var(--ok)} .import-msg.err{color:var(--bad)}

@media (max-width:900px){
  .practice-layout{grid-template-columns:1fr}
  .card-panel{position:static;order:2}
}
@media (max-width:640px){
  .topbar{padding:0 12px;gap:8px;height:56px}
  .brand{font-size:14px}
  .nav button{padding:6px 8px;font-size:13px}
  .mini-stat{display:none}
  .container{padding:16px 14px}
  .question-panel{padding:18px}
  .stem{font-size:16px}
  .hero{padding:22px} .hero h1{font-size:20px}
  .cat-row{grid-template-columns:84px 1fr 52px;gap:10px}
}
/* ============ 设置弹窗输入框 ============ */
.modal-box label{
  display:block;font-size:13px;color:var(--dim);margin:14px 0 6px;font-weight:500;
}
.modal-box input[type="text"],
.modal-box input[type="password"]{
  width:100%;font-family:inherit;font-size:14px;padding:9px 12px;
  border-radius:10px;border:1px solid var(--border);
  background:var(--panel-2);color:var(--text);outline:none;
}
.modal-box input[type="text"]:focus,
.modal-box input[type="password"]:focus{border-color:var(--primary);}
.modal-box .check-row{
  display:flex;align-items:center;gap:8px;margin-top:16px;
  font-size:14px;color:var(--text);cursor:pointer;
}
.modal-box .check-row input{width:auto;margin:0;cursor:pointer;}
.modal-box .code{
  font-family:ui-monospace,Menlo,Consolas,monospace;font-size:12px;
  background:var(--panel-2);border:1px solid var(--border);
  border-radius:5px;padding:1px 5px;
}

/* ============ AI 抽屉 ============ */
.ai-drawer{
  position:fixed;top:0;right:0;bottom:0;z-index:120;
  width:420px;max-width:94vw;
  background:var(--panel);border-left:1px solid var(--border);
  box-shadow:-12px 0 40px -18px rgba(0,0,0,.35);
  display:flex;flex-direction:column;
  transform:translateX(101%);transition:transform .26s cubic-bezier(.4,0,.2,1);
}
.ai-drawer.show{transform:translateX(0);}
.ai-head{
  display:flex;align-items:center;justify-content:space-between;
  padding:14px 18px;border-bottom:1px solid var(--border);
  font-weight:700;font-size:15px;flex:0 0 auto;
}
.ai-head button{
  border:none;background:transparent;font-size:17px;cursor:pointer;
  color:var(--dim);padding:2px 6px;line-height:1;border-radius:6px;
}
.ai-head button:hover{background:var(--panel-2);color:var(--text);}
.ai-ctx{
  flex:0 0 auto;padding:9px 18px;font-size:12px;color:var(--dim);
  border-bottom:1px solid var(--border);background:var(--panel-2);
  max-height:72px;overflow-y:auto;
}
.ai-msgs{
  flex:1;overflow-y:auto;padding:14px 18px;
  display:flex;flex-direction:column;gap:10px;
}
.ai-msg{font-size:14px;line-height:1.68;word-break:break-word;}
.ai-msg.user{
  align-self:flex-end;background:var(--primary-soft);color:var(--primary);
  padding:8px 14px;border-radius:12px 12px 2px 12px;max-width:84%;
  font-weight:500;
}
.ai-msg.bot{
  align-self:flex-start;background:var(--panel-2);border:1px solid var(--border);
  padding:10px 14px;border-radius:12px 12px 12px 2px;max-width:96%;
}
.ai-msg.bot .ai-code{
  background:var(--panel);border:1px solid var(--border);
  border-radius:8px;padding:8px 11px;margin:8px 0;
  font-family:ui-monospace,Menlo,Consolas,monospace;font-size:12.5px;
  overflow-x:auto;white-space:pre;line-height:1.55;
}
.ai-msg.bot .ai-inline{
  background:var(--panel);border:1px solid var(--border);
  border-radius:5px;padding:1px 5px;font-size:12.5px;
  font-family:ui-monospace,Menlo,Consolas,monospace;
}
.ai-msg.bot ul{margin:6px 0;padding-left:20px;}
.ai-msg.bot li{margin:2px 0;}
.ai-msg.err{color:var(--bad);background:var(--bad-soft);border-color:var(--bad);}
.ai-empty{
  margin:auto;text-align:center;color:var(--dim);font-size:13px;line-height:1.8;
}
.ai-empty .big{font-size:32px;display:block;margin-bottom:6px;}
.ai-typing::after{
  content:'▋';margin-left:2px;
  animation:aiBlink .85s steps(2) infinite;color:var(--primary);
}
@keyframes aiBlink{50%{opacity:0;}}
.ai-input-row{
  flex:0 0 auto;display:flex;gap:8px;padding:12px 14px;
  border-top:1px solid var(--border);align-items:flex-end;
}
.ai-input-row textarea{
  flex:1;resize:none;height:62px;font-family:inherit;font-size:14px;
  padding:9px 12px;border-radius:10px;border:1px solid var(--border);
  background:var(--panel-2);color:var(--text);outline:none;line-height:1.5;
}
.ai-input-row textarea:focus{border-color:var(--primary);}
.ai-input-row .btn{height:38px;}
@media (max-width:640px){
  .ai-drawer{width:100%;max-width:100%;}
}