:root{--color-bg: #f0f2f5;--color-card: #ffffff;--color-primary: #1890ff;--color-primary-hover: #40a9ff;--color-primary-light: #e6f7ff;--color-border: #e8e8e8;--color-text: #262626;--color-text-secondary: #595959;--color-text-muted: #8c8c8c;--color-success: #52c41a;--color-error: #ff4d4f;--radius: 12px;--radius-sm: 8px;--shadow: 0 2px 8px rgba(0, 0, 0, .06);--shadow-hover: 0 4px 16px rgba(0, 0, 0, .08);--max-width: 900px}*{box-sizing:border-box}body{margin:0;font-family:system-ui,Microsoft YaHei,PingFang SC,sans-serif;background:var(--color-bg);color:var(--color-text);line-height:1.6}#root{min-height:100vh;padding:2rem 1.5rem}.page{max-width:var(--max-width);margin:0 auto;display:flex;flex-direction:column;gap:1.5rem}.page h1{margin:0 0 .25rem;font-size:1.75rem;font-weight:600;color:var(--color-text)}.page>p:first-of-type{margin:0;color:var(--color-text-secondary);font-size:1rem}.card{background:var(--color-card);border-radius:var(--radius);box-shadow:var(--shadow);padding:2rem 2.25rem}.card--form{padding:2rem 2.25rem}.card--instructions .content{margin:0}.login-header{margin-bottom:1.5rem}.form-grid{display:grid;gap:1.5rem;max-width:480px}.form label{display:block;font-weight:500;color:var(--color-text);margin-bottom:.35rem;font-size:.95rem}.form input[type=text],.form select{width:100%;max-width:320px;padding:.65rem .85rem;border:1px solid var(--color-border);border-radius:var(--radius-sm);font-size:1rem;transition:border-color .2s,box-shadow .2s}.form input[type=text]:focus,.form select:focus{outline:none;border-color:var(--color-primary);box-shadow:0 0 0 2px #1890ff26}.radio-group{display:flex;gap:1.25rem;flex-wrap:wrap}.radio-group label{display:inline-flex;align-items:center;font-weight:400;cursor:pointer;padding:.4rem 0}.radio-group input{margin-right:.5rem;width:1rem;height:1rem;accent-color:var(--color-primary)}.instructions .content{margin:1.5rem 0;text-align:left}.instructions .content section{margin-bottom:1.75rem}.instructions .content section:last-child{margin-bottom:0}.instructions .content h3{font-size:1.05rem;font-weight:600;color:var(--color-text);margin:0 0 .5rem}.instructions .content p,.instructions .content ul{margin:0 0 .5rem;color:var(--color-text-secondary);font-size:1rem;line-height:1.7}.instructions .content ul{padding-left:1.35rem}.instructions .content li{margin-bottom:.35rem}.btn{padding:.6rem 1.25rem;cursor:pointer;border-radius:var(--radius-sm);border:1px solid var(--color-border);background:var(--color-card);font-size:1rem;font-weight:500;transition:background .2s,border-color .2s,box-shadow .2s}.btn:hover:not(:disabled){border-color:var(--color-primary);color:var(--color-primary);background:var(--color-primary-light)}.btn.primary{background:var(--color-primary);color:#fff;border-color:var(--color-primary)}.btn.primary:hover:not(:disabled){background:var(--color-primary-hover);border-color:var(--color-primary-hover);color:#fff;box-shadow:0 2px 8px #1890ff59}.btn.primary:disabled{opacity:.65;cursor:not-allowed}.btn.large{padding:.85rem 1.75rem;font-size:1.05rem}.actions{display:flex;gap:1rem;flex-wrap:wrap;margin-top:.5rem}.phase-hint{color:var(--color-text-muted);font-size:.95rem;margin:0 0 .5rem}.tip{color:var(--color-text-muted);font-size:.9rem;margin-top:1rem}.question-card{text-align:left}.q-meta{color:var(--color-text-muted);font-size:.9rem;margin-bottom:1rem;font-weight:500}.q-stem{font-size:1.2rem;line-height:1.7;margin-bottom:1.5rem;color:var(--color-text)}.options{list-style:none;padding:0;margin:0 0 1.75rem;display:flex;flex-direction:column;gap:.85rem}.option-card{display:block;text-align:left;padding:1rem 1.25rem;border:2px solid var(--color-border);border-radius:var(--radius-sm);cursor:pointer;transition:border-color .2s,background .2s,box-shadow .2s;background:var(--color-card)}.option-card:hover{border-color:var(--color-primary);background:var(--color-primary-light);box-shadow:var(--shadow)}.option-card.selected{border-color:var(--color-primary);background:var(--color-primary-light);box-shadow:0 0 0 1px var(--color-primary)}.option-card input{position:absolute;opacity:0;pointer-events:none}.option-card .opt-row{display:flex;align-items:flex-start;gap:.75rem}.opt-label{flex-shrink:0;width:1.75rem;height:1.75rem;display:inline-flex;align-items:center;justify-content:center;font-weight:600;font-size:.95rem;color:var(--color-primary);border:2px solid var(--color-primary);border-radius:50%;line-height:1}.option-card.selected .opt-label{background:var(--color-primary);color:#fff}.opt-text{flex:1;font-size:1.05rem;line-height:1.6;color:var(--color-text)}.feedback{text-align:left}.feedback .correct,.feedback .wrong{font-size:1.15rem;font-weight:600;margin:0 0 1rem}.feedback .correct{color:var(--color-success)}.feedback .wrong{color:var(--color-error)}.feedback .explanation{margin:1.25rem 0;padding:1.25rem;background:var(--color-bg);border-radius:var(--radius-sm);border-left:4px solid var(--color-primary)}.feedback .explanation strong{color:var(--color-text)}.feedback .explanation p{margin:.5rem 0 0;line-height:1.7;color:var(--color-text-secondary)}.error-msg{color:var(--color-error);margin:.5rem 0 0}.success-msg{color:var(--color-success);font-weight:600;margin:1rem 0 0}.completion .actions .btn.primary.large{margin-top:0}.card .question-card{background:transparent;box-shadow:none;padding:0;border-radius:0}.card .question-card .btn.primary{margin-top:.25rem}.login .card:first-of-type{margin-top:0}.login .page>h1{margin-bottom:.5rem}.instructions .card{margin-top:0}.instructions .page>.btn{align-self:flex-start}.completion .card{margin-top:0}@media (max-width: 640px){#root{padding:1rem}.card,.page .question-card{padding:1.5rem 1.25rem}.q-stem{font-size:1.1rem}.opt-text{font-size:1rem}}