*{box-sizing:border-box;margin:0;padding:0}:root{--primary-color:#2196f3;--success-color:#4caf50;--warning-color:#ff9800;--danger-color:#f44336;--text-primary:#333;--text-secondary:#666;--text-light:#999;--bg-color:#f5f7fa;--card-bg:#fff;--border-color:#e0e0e0}body{background:var(--bg-color);color:var(--text-primary);-webkit-font-smoothing:antialiased;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,sans-serif;line-height:1.6}#app{min-height:100vh;padding-bottom:70px}.bottom-nav{background:var(--card-bg);border-top:1px solid var(--border-color);z-index:1000;justify-content:space-around;padding:8px 0;display:flex;position:fixed;bottom:0;left:0;right:0}.nav-item{color:var(--text-light);flex-direction:column;align-items:center;padding:4px 12px;font-size:12px;text-decoration:none;display:flex}.nav-item.active{color:var(--primary-color)}.nav-icon{margin-bottom:2px;font-size:24px}.container{max-width:800px;margin:0 auto;padding:16px}.card{background:var(--card-bg);border-radius:12px;margin-bottom:16px;padding:16px;box-shadow:0 2px 8px #0000000d}.page-title{color:var(--text-primary);margin-bottom:20px;font-size:24px;font-weight:600}.btn{cursor:pointer;border:none;border-radius:8px;justify-content:center;align-items:center;padding:12px 24px;font-size:14px;font-weight:500;transition:all .2s;display:inline-flex}.btn-primary{background:var(--primary-color);color:#fff}.btn-primary:hover{background:#1976d2}.btn-success{background:var(--success-color);color:#fff}.btn-outline{border:2px solid var(--primary-color);color:var(--primary-color);background:0 0}.btn-block{width:100%}.tag{border-radius:4px;padding:4px 12px;font-size:12px;font-weight:500;display:inline-block}.tag-single{color:#1976d2;background:#e3f2fd}.tag-multi{color:#f57c00;background:#fff3e0}.tag-judge{color:#388e3c;background:#e8f5e9}.loading{flex-direction:column;justify-content:center;align-items:center;padding:40px;display:flex}.spinner{border:3px solid var(--border-color);border-top-color:var(--primary-color);border-radius:50%;width:40px;height:40px;animation:.8s linear infinite spin}@keyframes spin{to{transform:rotate(360deg)}}.empty-state{text-align:center;color:var(--text-light);padding:60px 20px}.empty-icon{margin-bottom:16px;font-size:64px}.options-list{flex-direction:column;gap:12px;display:flex}.option-item{background:var(--bg-color);cursor:pointer;border:2px solid #0000;border-radius:8px;align-items:flex-start;padding:12px 16px;transition:all .2s;display:flex}.option-item:hover{background:#e3f2fd}.option-item.active{border-color:var(--primary-color);background:#e3f2fd}.option-item.correct{border-color:var(--success-color);background:#e8f5e9}.option-item.wrong{border-color:var(--danger-color);background:#ffebee}.option-letter{background:var(--card-bg);border-radius:50%;flex-shrink:0;justify-content:center;align-items:center;width:28px;height:28px;margin-right:12px;font-weight:600;display:flex}.option-text{flex:1;font-size:14px;line-height:1.6}@media (width>=768px){.container{padding:24px}.bottom-nav{border-radius:16px 16px 0 0;max-width:800px;left:50%;transform:translate(-50%)}}