:root{
  --bg:#f3f5f9; --card:#fff; --line:#e7eaf0; --ink:#1d2129; --muted:#8a9099;
  --blue:#2f7af6; --blue-d:#1f63d8; --green:#22a06b; --amber:#e8950c; --red:#e5484d;
  --shadow:0 2px 10px rgba(20,40,80,.06);
}
*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}
html,body{margin:0;height:100%}
body{font-family:-apple-system,BlinkMacSystemFont,'PingFang SC','Microsoft YaHei',sans-serif;
  background:var(--bg);color:var(--ink);font-size:16px;line-height:1.6;overscroll-behavior:none}
a{color:inherit;text-decoration:none}
.hidden{display:none!important}
.wrap{max-width:760px;margin:0 auto;padding:16px}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;border:none;border-radius:12px;
  padding:13px 18px;font-size:16px;font-weight:600;background:var(--blue);color:#fff;cursor:pointer;transition:.15s}
.btn:active{transform:scale(.98)}
.btn.block{width:100%}
.btn.ghost{background:#eef2f8;color:#3a4252}
.btn.green{background:var(--green)} .btn.red{background:var(--red)} .btn.amber{background:var(--amber)}
.btn.sm{padding:7px 12px;font-size:13px;border-radius:9px}
.btn:disabled{opacity:.5;cursor:not-allowed}
.input{width:100%;border:1.5px solid var(--line);border-radius:12px;padding:13px 14px;font-size:16px;background:#fff;margin:6px 0}
.input:focus{outline:none;border-color:var(--blue)}
.card{background:var(--card);border:1px solid var(--line);border-radius:16px;padding:16px;box-shadow:var(--shadow);margin-bottom:14px}
.tag{display:inline-block;font-size:12px;padding:2px 9px;border-radius:20px;background:#eef1f5;color:#5a6472}
.tag.blue{background:#e8f1ff;color:var(--blue)} .tag.green{background:#e6f7ef;color:var(--green)}
.tag.amber{background:#fdf2dd;color:var(--amber)} .tag.red{background:#fdecec;color:var(--red)}
.muted{color:var(--muted)}
.row{display:flex;gap:10px;align-items:center}
.spread{display:flex;justify-content:space-between;align-items:center}
h1{font-size:22px;margin:0 0 4px} h2{font-size:18px;margin:0 0 10px}
.toast{position:fixed;left:50%;bottom:80px;transform:translateX(-50%);background:#222d;color:#fff;
  padding:10px 16px;border-radius:10px;font-size:14px;z-index:99;opacity:0;transition:.25s;pointer-events:none}
.toast.show{opacity:1;bottom:96px}

/* landing */
.land{min-height:100%;display:flex;flex-direction:column;justify-content:center;align-items:center;gap:18px;padding:24px;text-align:center}
.land .logo{font-size:30px;font-weight:800;letter-spacing:1px;color:var(--blue)}
.role{width:100%;max-width:340px;border-radius:18px;padding:26px 20px;color:#fff;font-size:20px;font-weight:700;
  box-shadow:var(--shadow);display:flex;align-items:center;gap:14px;cursor:pointer;transition:.15s}
.role:active{transform:scale(.98)}
.role .ico{font-size:34px}
.role.stu{background:linear-gradient(135deg,#3b8cff,#2f6bf6)}
.role.tea{background:linear-gradient(135deg,#22b07d,#179467)}
.role small{display:block;font-size:13px;font-weight:400;opacity:.9;margin-top:2px}

/* topbar */
.topbar{position:sticky;top:0;z-index:20;background:#fff;border-bottom:1px solid var(--line);
  display:flex;align-items:center;gap:10px;padding:10px 14px}
.topbar .title{font-weight:700;font-size:15px;flex:1;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.timer{font-variant-numeric:tabular-nums;font-weight:700;color:var(--blue);background:#eef4ff;padding:4px 10px;border-radius:8px;font-size:14px}

/* options */
.opt{display:flex;gap:10px;align-items:flex-start;border:1.5px solid var(--line);border-radius:12px;padding:12px 14px;margin:8px 0;cursor:pointer;background:#fff;transition:.12s}
.opt:active{background:#f7f9fc}
.opt .k{flex:0 0 24px;height:24px;border-radius:50%;background:#eef1f5;color:#5a6472;display:flex;align-items:center;justify-content:center;font-weight:700;font-size:13px}
.opt.sel{border-color:var(--blue);background:#eff5ff}
.opt.sel .k{background:var(--blue);color:#fff}
.opt.correct{border-color:var(--green);background:#edf9f2}
.opt.correct .k{background:var(--green);color:#fff}
.opt.wrong{border-color:var(--red);background:#fdecec}
.opt.wrong .k{background:var(--red);color:#fff}

.material{font-size:14px;color:#475;background:#f6f8fb;border-left:3px solid #c7d2e0;padding:10px 12px;border-radius:8px;margin-bottom:10px;white-space:pre-wrap}
.stem{font-weight:600;font-size:17px;margin:6px 0 8px;white-space:pre-wrap}
.fig{margin:8px 0;text-align:center}
.fig img{max-width:100%;border:1px solid var(--line);border-radius:10px;background:#fff}
.exp{margin-top:10px;background:#f3f9f5;border:1px solid #d9eee2;border-radius:10px;padding:10px 12px;font-size:14px}
.exp b{color:var(--green)}

/* sheet (答题卡) */
.sheet-mask{position:fixed;inset:0;background:#0006;z-index:30;opacity:0;pointer-events:none;transition:.2s}
.sheet-mask.show{opacity:1;pointer-events:auto}
.sheet{position:fixed;left:0;right:0;bottom:0;background:#fff;border-radius:18px 18px 0 0;z-index:31;
  transform:translateY(100%);transition:.25s;max-height:70vh;overflow:auto;padding:16px}
.sheet.show{transform:translateY(0)}
.grid{display:grid;grid-template-columns:repeat(6,1fr);gap:10px;margin-top:10px}
.cell{aspect-ratio:1;border-radius:10px;border:1.5px solid var(--line);display:flex;align-items:center;justify-content:center;font-weight:700;cursor:pointer;background:#fff}
.cell.done{background:#eff5ff;border-color:var(--blue);color:var(--blue)}
.cell.cur{background:var(--blue);border-color:var(--blue);color:#fff}
.cell.correct{background:#e6f7ef;border-color:var(--green);color:var(--green)}
.cell.wrong{background:#fdecec;border-color:var(--red);color:var(--red)}

/* bottom nav */
.bottomnav{position:sticky;bottom:0;background:#fff;border-top:1px solid var(--line);display:flex;gap:10px;padding:10px 14px}
.bottomnav .btn{flex:1}

/* result */
.score-ring{width:130px;height:130px;border-radius:50%;margin:6px auto;display:flex;flex-direction:column;align-items:center;justify-content:center;
  background:conic-gradient(var(--blue) calc(var(--p)*1%), #e9eef6 0);}
.score-ring .inner{width:104px;height:104px;border-radius:50%;background:#fff;display:flex;flex-direction:column;align-items:center;justify-content:center}
.score-ring .num{font-size:34px;font-weight:800;color:var(--blue);line-height:1}

/* figure display + zoom */
.fig img{cursor:zoom-in}
.lightbox{position:fixed;inset:0;background:#000d;z-index:80;display:none;align-items:center;justify-content:center;flex-direction:column;gap:12px}
.lightbox.show{display:flex}
.lightbox img{max-width:96vw;max-height:82vh;border-radius:8px;background:#fff;touch-action:none;transition:transform .05s}
.lightbox .lbbar{display:flex;gap:10px}
.lightbox .lbbar .btn{background:#ffffff22;backdrop-filter:blur(4px)}

/* figure editor */
.fed{position:fixed;inset:0;background:#0009;z-index:90;display:none}
.fed.show{display:flex;flex-direction:column}
.fed .top{background:#fff;padding:10px 14px;display:flex;align-items:center;gap:10px;border-bottom:1px solid var(--line)}
.fed .top b{flex:1;font-size:15px}
.fed .tabs{display:flex;gap:8px;padding:8px 14px;background:#fff}
.fed .tabs .p{padding:7px 14px;border-radius:20px;border:1.5px solid var(--line);background:#fff;cursor:pointer;font-size:14px}
.fed .tabs .p.on{border-color:var(--blue);background:#eff5ff;color:var(--blue);font-weight:600}
.fed .stage{flex:1;overflow:auto;background:#222;display:flex;align-items:flex-start;justify-content:center;padding:10px}
.fed .canwrap{position:relative;line-height:0}
.fed canvas{max-width:100%;touch-action:none;background:#fff}
.fed .crop{position:absolute;border:2px solid #2f7af6;background:#2f7af622;box-sizing:border-box;pointer-events:none}
.fed .bottom{background:#fff;padding:10px 14px;display:flex;gap:8px;align-items:center;flex-wrap:wrap;border-top:1px solid var(--line)}
.fed .hint{font-size:12px;color:var(--muted);flex-basis:100%}
.fed .prev{height:60px;border:1px solid var(--line);border-radius:6px;background:#fff}

/* table */
table{width:100%;border-collapse:collapse;font-size:14px}
th,td{padding:9px 8px;border-bottom:1px solid var(--line);text-align:left}
th{color:var(--muted);font-weight:600;font-size:13px}
.bar{height:8px;border-radius:6px;background:#eef1f5;overflow:hidden}
.bar>i{display:block;height:100%;background:var(--green)}