:root{--bg: #F0F4F8;--surface: #FFFFFF;--surface2: #EEF2F7;--border: #DDE3ED;--text: #0F172A;--text-muted: #64748B;--text-dim: #94A3B8;--micro: #3B82F6;--macro: #8B5CF6;--calc: #14B8A6;--correct: #16A34A;--incorrect: #DC2626;--warning: #F59E0B;--yellow: #EAB308;--subject-clr: var(--micro);--radius: 16px;--radius-sm: 12px;--shadow: 0 2px 12px rgba(0,0,0,.08);--transition: .18s ease}*,*:before,*:after{box-sizing:border-box;margin:0;padding:0}html,body{height:100%;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif;background:var(--bg);color:var(--text);line-height:1.5}button{cursor:pointer;border:none;background:none;color:inherit;font:inherit}input,select,textarea{font:inherit}.btn{padding:12px 20px;border-radius:var(--radius-sm);font-weight:600;font-size:15px;transition:var(--transition);display:inline-flex;align-items:center;justify-content:center;gap:6px}.btn-primary{background:var(--subject-clr);color:#fff}.btn-primary:hover{filter:brightness(1.12)}.btn-outline{border:1.5px solid var(--border);color:var(--text)}.btn-outline:hover{background:var(--surface2)}.btn-full{width:100%}.btn-sm{padding:8px 14px;font-size:13px}.btn:disabled{opacity:.45;cursor:not-allowed}.sheet-overlay{position:fixed;inset:0;background:#0009;display:flex;align-items:center;justify-content:center;z-index:100;-webkit-backdrop-filter:blur(2px);backdrop-filter:blur(2px);animation:fadeIn .15s ease;padding:16px}.sheet{background:var(--surface);border-radius:20px;width:100%;max-width:480px;max-height:90vh;overflow-y:auto;animation:scaleIn .2s ease}.sheet-full{max-height:95vh;max-width:560px}.sheet-header{display:flex;align-items:center;gap:12px;padding:20px 20px 16px;border-bottom:1px solid var(--border);position:sticky;top:0;background:var(--surface);z-index:5}.sheet-header h2{flex:1;font-size:20px}.close-btn{font-size:20px;color:var(--text-muted);padding:4px 8px;line-height:1}.sheet-footer{padding:16px 20px;border-top:1px solid var(--border);display:flex;gap:10px}@keyframes fadeIn{0%{opacity:0}to{opacity:1}}@keyframes slideUp{0%{transform:translateY(60px);opacity:0}to{transform:translateY(0);opacity:1}}@keyframes scaleIn{0%{transform:scale(.85);opacity:0}to{transform:scale(1);opacity:1}}.ring-bg{fill:none;stroke:var(--surface2);stroke-width:10}.ring-progress{fill:none;stroke-width:10;stroke-linecap:round;transition:stroke-dashoffset .6s ease,stroke .4s ease}.option-btn{display:flex;align-items:center;gap:14px;padding:14px 16px;border-radius:var(--radius);border:1.5px solid var(--border);background:var(--surface2);text-align:left;font-size:15px;transition:var(--transition);color:var(--text);width:100%}.option-btn:hover:not(:disabled):not(.correct):not(.incorrect){border-color:var(--subject-clr)}.option-btn.selected{border-color:var(--subject-clr);border-width:2px;background:#fff}.option-btn.selected .option-letter{background:var(--subject-clr);color:#fff;border-color:var(--subject-clr)}.option-btn.selected span:last-child{font-weight:700}.option-btn.correct{border-color:var(--correct);border-width:2px;background:#f0fdf4;color:var(--text)}.option-btn.correct .option-letter{background:var(--correct);color:#fff;border-color:var(--correct)}.option-btn.incorrect{border-color:var(--incorrect);border-width:2px;background:#fef2f2;color:var(--text)}.option-btn.incorrect .option-letter{background:var(--incorrect);color:#fff;border-color:var(--incorrect)}.option-letter{width:34px;height:34px;min-width:34px;border-radius:50%;background:#dde3ed;border:none;display:flex;align-items:center;justify-content:center;font-size:13px;font-weight:700;color:var(--text-muted);transition:var(--transition)}.empty-state{text-align:center;padding:48px 20px;color:var(--text-muted)}.empty-icon{font-size:48px;margin-bottom:12px}::-webkit-scrollbar{width:6px}::-webkit-scrollbar-thumb{background:var(--border);border-radius:3px}