:root{
  --bg:#f7f8fc;
  --panel:#ffffff;
  --panel-soft:#f3f5fa;
  --line:#e2e7f0;
  --text:#263246;
  --muted:#748096;
  --primary:#6f63df;
  --primary-dark:#5f54c9;
  --success:#2f9b72;
  --success-soft:#eaf8f1;
  --danger:#d86472;
  --danger-soft:#fff0f2;
  --warning:#c58a2c;
  --warning-soft:#fff7e7;
  --info:#5e83c8;
  --info-soft:#edf4ff;
  --shadow:0 12px 30px rgba(54,64,96,.08);
}

*{box-sizing:border-box}
html,body{margin:0;min-height:100%}
body{
  min-height:100vh;
  background:
    radial-gradient(circle at 10% 0%,rgba(130,111,227,.09),transparent 26%),
    radial-gradient(circle at 96% 5%,rgba(255,180,205,.10),transparent 28%),
    var(--bg);
  color:var(--text);
  font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;
}
a{color:inherit}

.work-shell{
  width:min(760px,calc(100% - 20px));
  margin:0 auto;
  padding:16px 0 90px;
}

.work-card{
  background:var(--panel);
  border:1px solid var(--line);
  border-radius:22px;
  box-shadow:var(--shadow);
  padding:18px;
  margin-bottom:14px;
}

.work-card.soft{background:var(--panel-soft)}
.work-head{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:12px;
  margin-bottom:14px;
}
.back-link{
  display:inline-flex;align-items:center;gap:5px;
  text-decoration:none;color:var(--muted);
  font-size:12px;font-weight:800;
}
.back-link:hover{color:var(--primary)}
.badge{
  display:inline-flex;align-items:center;gap:5px;
  padding:6px 9px;border-radius:999px;
  font-size:10px;font-weight:900;letter-spacing:.05em;text-transform:uppercase;
  background:#f0efff;color:var(--primary);
}
.badge.homework{background:#fff1dc;color:#a96f1d}
.badge.quiz{background:#ffe9ef;color:#c05369}
.badge.review{background:#fff4d9;color:#9b6b14}
.title{
  margin:0;color:var(--text);font-size:22px;line-height:1.25;letter-spacing:-.02em;
}
.subtle{color:var(--muted);font-size:11px;line-height:1.55}
.progress-row{display:flex;align-items:center;gap:10px;margin-top:12px}
.progress-track{flex:1;height:9px;border-radius:999px;background:#edf0f5;overflow:hidden}
.progress-fill{height:100%;background:linear-gradient(90deg,var(--primary),#9d84ef);border-radius:999px}
.progress-value{min-width:38px;text-align:right;font-size:12px;font-weight:900;color:var(--primary)}

.notice{
  margin-top:12px;padding:12px 13px;border-radius:14px;border:1px solid var(--line);
  font-size:11px;line-height:1.5;
}
.notice.info{background:var(--info-soft);border-color:#d8e6ff;color:#4f6e9d}
.notice.warning{background:var(--warning-soft);border-color:#f0ddb6;color:#8a641f}
.notice.success{background:var(--success-soft);border-color:#cfeede;color:#39795f}
.notice.danger{background:var(--danger-soft);border-color:#f2cfd5;color:#a04c58}

.btn{
  appearance:none;border:0;cursor:pointer;text-decoration:none;
  display:inline-flex;align-items:center;justify-content:center;gap:7px;
  min-height:44px;padding:11px 14px;border-radius:14px;
  font-size:12px;font-weight:900;transition:.16s ease;
}
.btn:hover{transform:translateY(-1px)}
.btn:active{transform:translateY(0)}
.btn-primary{background:var(--primary);color:#fff;box-shadow:0 8px 18px rgba(111,99,223,.18)}
.btn-dark{background:#273246;color:#fff}
.btn-soft{background:#eef0f6;color:#556079}
.btn-success{background:var(--success);color:#fff}
.btn-warning{background:#e0a443;color:#fff}
.btn-full{width:100%}
.btn[disabled]{opacity:.55;cursor:not-allowed;transform:none}

.start-card{text-align:center;padding:26px 20px}
.start-card .emoji{font-size:48px;margin-bottom:10px}
.start-card h2{margin:0 0 8px;font-size:22px}
.start-card p{margin:0 auto 20px;max-width:520px;color:var(--muted);font-size:12px;line-height:1.6}

.questions-list{display:grid;gap:14px}
.question-list-card{
  background:var(--panel);border:1px solid var(--line);border-radius:20px;padding:16px;
  box-shadow:0 8px 22px rgba(60,70,100,.05)
}
.question-list-card.correct{background:#f4fbf7;border-color:#cfe9db}
.question-list-card.wrong{background:#fff6f7;border-color:#efd3d8}
.question-list-card.answered{background:#f3f2ff;border-color:#dad5ff}
.question-list-card.hint{background:#fffaf0;border-color:#f0dfbd}
.q-head{
  display:flex;align-items:center;justify-content:space-between;gap:10px;
  padding-bottom:10px;margin-bottom:12px;border-bottom:1px solid #edf0f5;
}
.q-no,.difficulty{
  display:inline-flex;padding:4px 7px;border-radius:8px;background:#fff;border:1px solid #e8ebf1;
  font-size:10px;font-weight:900
}
.status{font-size:10px;font-weight:800}
.question-text{font-size:14px;line-height:1.7}
.option-preview{
  margin-top:7px;padding:10px 11px;border:1px solid #ebedf3;border-radius:12px;
  background:#f8f9fc;color:#667086;font-size:12px
}
.option-preview.correct{background:#eaf8f1;border-color:#c9ead8;color:#37765d;font-weight:800}
.option-preview.wrong{background:#fff0f2;border-color:#efcbd1;color:#a34c59;font-weight:800}
.option-preview.selected{background:#eef0f5;border-color:#cbd1db;color:#374155;font-weight:800}

.solve-card{
  background:#fff;border:1px solid var(--line);border-radius:22px;padding:18px;
  box-shadow:var(--shadow);margin-bottom:80px;
}
.solve-top{
  display:flex;align-items:center;justify-content:space-between;gap:10px;
  padding-bottom:12px;margin-bottom:16px;border-bottom:1px solid var(--line)
}
.timer{
  padding:7px 10px;border-radius:999px;background:#eef0ff;color:var(--primary);
  border:1px solid #d9d5ff;font-family:ui-monospace,SFMono-Regular,Menlo,monospace;
  font-size:13px;font-weight:900
}
.timer.danger{background:var(--danger-soft);color:var(--danger);border-color:#f0c8cf}
.solve-question{font-size:15px;line-height:1.75;margin-bottom:16px}
.options{display:grid;gap:9px}
.option-btn{
  width:100%;display:flex;align-items:flex-start;gap:10px;text-align:left;
  padding:13px;border:2px solid #e7eaf1;border-radius:15px;background:#fff;color:#4c566b;
  font:inherit;font-size:13px;cursor:pointer;transition:.15s ease
}
.option-btn:hover{border-color:#bfb6fb;background:#faf9ff}
.option-btn.selected{background:#f0edff;border-color:#9d90ef;color:#5b4ed0;font-weight:800}
.option-btn.correct{background:var(--success-soft);border-color:#72c6a1;color:#2f775a;font-weight:900}
.option-btn.wrong{background:var(--danger-soft);border-color:#e39aa5;color:#a04c58;font-weight:900}
.option-btn.muted{opacity:.48;background:#f6f7f9}
.option-icon{font-size:18px;line-height:1.2}
.feedback{
  margin-top:13px;padding:13px;border-radius:14px;border:1px solid var(--line);
  font-size:12px;line-height:1.6
}
.feedback.hidden{display:none}
.feedback.wrong{background:var(--danger-soft);border-color:#f0cbd1;color:#984753}
.feedback.success{background:var(--success-soft);border-color:#cfeade;color:#33745a}
.hints{display:grid;gap:9px;margin-top:14px}
.hint-box{
  padding:12px;border:1px solid #d9d7ff;border-radius:14px;background:#f2f1ff;color:#5c56a5;
  font-size:12px;line-height:1.55
}
.solution{
  margin-top:18px;padding:15px;border-radius:18px;background:#2b3445;color:#e9edf5
}
.solution h3{margin:0 0 12px;color:#ffd36b;font-size:13px}
.solution-step{display:flex;gap:10px;padding:11px;border-radius:13px;background:rgba(255,255,255,.06);margin-bottom:8px}
.solution-step .n{width:26px;height:26px;display:grid;place-items:center;border-radius:50%;background:#7568e6;color:#fff;font-size:11px;font-weight:900}
.solution-step h4{margin:0 0 3px;font-size:12px}
.solution-step p{margin:0;color:#c5ccda;font-size:12px;line-height:1.5}

.scratch-btn{
  position:fixed;right:18px;bottom:18px;width:52px;height:52px;border:0;border-radius:50%;
  background:var(--primary);color:#fff;box-shadow:0 10px 24px rgba(111,99,223,.28);
  cursor:pointer;z-index:40;font-size:22px
}
.scratch{
  position:fixed;inset:0;display:none;flex-direction:column;background:rgba(255,255,255,.96);
  backdrop-filter:blur(8px);z-index:50
}
.scratch.open{display:flex}
.scratch-head{
  display:flex;justify-content:space-between;align-items:center;gap:8px;padding:10px;
  border-bottom:1px solid var(--line);background:#fff
}
.scratch-actions{display:flex;gap:6px;flex-wrap:wrap}
.scratch-actions button{border:0;padding:7px 9px;border-radius:10px;background:#eef0f5;color:#465168;font-size:11px;font-weight:800}
.scratch-actions .close{background:var(--primary);color:#fff}
#drawing-board{flex:1;width:100%;height:100%;touch-action:none}

.result-wrap{width:min(760px,calc(100% - 20px));margin:0 auto;padding:16px 0 60px}
.result-hero{
  text-align:center;padding:22px;border:1px solid var(--line);border-radius:22px;background:#fff;box-shadow:var(--shadow)
}
.score-ring{
  width:132px;height:132px;margin:16px auto;border-radius:50%;display:grid;place-items:center;position:relative;
}
.score-ring::after{content:"";position:absolute;inset:14px;background:#fff;border-radius:50%}
.score-inner{position:relative;z-index:1;text-align:center}
.score-inner small{display:block;color:var(--muted);font-size:9px;font-weight:900}
.score-inner b{display:block;font-size:34px}
.net-box{display:inline-flex;align-items:center;gap:6px;padding:10px 12px;border-radius:14px;background:#f5f6fa;color:#657086;font-size:12px;font-weight:800}

.analysis-grid{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin-top:14px}
.analysis-card{padding:14px;border:1px solid var(--line);border-radius:18px;background:#fff}
.analysis-card.soft{background:#f3f5f8}
.analysis-card h3{margin:0 0 10px;font-size:12px}
.metric-big{font-size:28px;font-weight:900}
.signal{margin-top:7px;padding:9px;border-radius:12px;font-size:10px;line-height:1.4}
.signal.rose{background:#fff0f2;color:#9d4a56}
.signal.orange{background:#fff4e9;color:#9c642a}
.signal.blue{background:#eef4ff;color:#5270a5}
.signal.cyan{background:#ebf9fb;color:#4c7c84}
.signal.purple{background:#f1edff;color:#6557b7}
.signal.amber{background:#fff7e7;color:#8d691f}
.signal.green{background:#eaf8f1;color:#37765d}
.coach-note{margin-top:12px;padding:13px;border-radius:16px;background:#f0edff;color:#5a55a6;font-size:11px;line-height:1.55}

.student-toast-container{
  position:fixed;left:50%;top:max(14px,env(safe-area-inset-top));transform:translateX(-50%);
  width:min(460px,calc(100% - 20px));display:grid;gap:8px;z-index:1000;pointer-events:none
}
.student-toast{
  pointer-events:auto;padding:12px 14px;border-radius:14px;background:#fff;border:1px solid var(--line);
  box-shadow:0 14px 34px rgba(43,50,75,.18);font-size:12px;line-height:1.45;
  animation:toastIn .2s ease
}
.student-toast.success{background:var(--success-soft);border-color:#cfeade;color:#35765c}
.student-toast.error{background:var(--danger-soft);border-color:#efcbd1;color:#9c4b57}
.student-toast.warning{background:var(--warning-soft);border-color:#f0ddb6;color:#8b661f}
@keyframes toastIn{from{opacity:0;transform:translateY(-8px)}to{opacity:1;transform:translateY(0)}}

.student-modal-backdrop{
  position:fixed;inset:0;background:rgba(27,34,50,.38);backdrop-filter:blur(3px);
  display:none;align-items:center;justify-content:center;padding:18px;z-index:1100
}
.student-modal-backdrop.open{display:flex}
.student-modal{
  width:min(420px,100%);background:#fff;border:1px solid var(--line);border-radius:20px;
  box-shadow:0 20px 55px rgba(30,36,55,.25);padding:18px
}
.student-modal h3{margin:0 0 7px;font-size:17px}
.student-modal p{margin:0;color:var(--muted);font-size:12px;line-height:1.55}
.student-modal-actions{display:flex;justify-content:flex-end;gap:8px;margin-top:16px}

@media(max-width:640px){
  .work-shell,.result-wrap{width:min(100% - 14px,760px)}
  .work-card,.solve-card{border-radius:18px;padding:14px}
  .title{font-size:19px}
  .analysis-grid{grid-template-columns:1fr}
  .q-head{align-items:flex-start}
}
.student-choice-note{
  margin-left:6px;
  color:var(--primary);
  font-size:10px;
  font-weight:900;
}