*,*:before,*:after{box-sizing:border-box;margin:0;padding:0}:root{--bg-primary: #ffffff;--bg-secondary: #f5f5f3;--bg-info: #e6f1fb;--bg-success: #eaf3de;--bg-danger: #fcebeb;--text-primary: #1a1a18;--text-secondary: #5f5e5a;--text-tertiary: #888780;--text-info: #185fa5;--text-success: #27500a;--text-danger: #791f1f;--border: rgba(0,0,0,.15);--border-md: rgba(0,0,0,.25);--radius-md: 8px;--radius-lg: 12px;--blue: #185fa5;--blue-light: #e6f1fb;--green: #639922;--red: #e24b4a}@media (prefers-color-scheme: dark){:root{--bg-primary: #1c1c1a;--bg-secondary: #2a2a27;--bg-info: #0c447c;--bg-success: #17340a;--bg-danger: #501313;--text-primary: #f0ede6;--text-secondary: #b4b2a9;--text-tertiary: #888780;--text-info: #85b7eb;--text-success: #97c459;--text-danger: #f09595;--border: rgba(255,255,255,.12);--border-md: rgba(255,255,255,.22);--blue: #378add;--blue-light: #042c53;--green: #97c459;--red: #f09595}}body{font-family:-apple-system,BlinkMacSystemFont,Hiragino Sans,Noto Sans JP,sans-serif;background:var(--bg-secondary);color:var(--text-primary);min-height:100vh;padding:1.5rem 1rem}#app{max-width:680px;margin:0 auto}.header{display:flex;align-items:center;justify-content:space-between;margin-bottom:1.5rem}.header h1{font-size:20px;font-weight:500;display:flex;align-items:center;gap:8px}.header h1 i{color:var(--blue);font-size:22px}.badge{font-size:12px;background:var(--bg-info);color:var(--text-info);padding:4px 12px;border-radius:var(--radius-md)}.stats{display:grid;grid-template-columns:repeat(3,1fr);gap:8px;margin-bottom:1.25rem}.stat{background:var(--bg-primary);border:.5px solid var(--border);border-radius:var(--radius-md);padding:12px 16px;text-align:center}.stat-label{font-size:12px;color:var(--text-secondary);margin-bottom:4px}.stat-val{font-size:24px;font-weight:500}.stat-val.good{color:var(--green)}.progress-bar{height:4px;background:var(--border);border-radius:2px;margin-bottom:1.25rem;overflow:hidden}.progress-fill{height:100%;background:var(--blue);border-radius:2px;transition:width .4s ease}.category-bar{display:flex;flex-wrap:wrap;gap:6px;margin-bottom:1.25rem}.cat-btn{font-size:12px;padding:5px 12px;border-radius:20px;border:.5px solid var(--border-md);background:var(--bg-primary);color:var(--text-secondary);cursor:pointer;transition:all .15s;font-family:inherit}.cat-btn:hover{background:var(--bg-secondary)}.cat-btn.active{background:var(--blue-light);color:var(--text-info);border-color:var(--blue)}.problem-card{background:var(--bg-primary);border:.5px solid var(--border);border-radius:var(--radius-lg);padding:1.5rem;margin-bottom:1rem;min-height:180px}.problem-cat{font-size:11px;color:var(--text-tertiary);margin-bottom:10px;letter-spacing:.06em;text-transform:uppercase}.problem-text{font-size:15px;line-height:1.9;color:var(--text-primary)}.answer-area{margin-top:1.25rem}.answer-row{display:flex;align-items:center;gap:8px;margin-bottom:10px}.answer-label{font-size:13px;color:var(--text-secondary);min-width:28px}.answer-input{flex:1;padding:9px 14px;border:.5px solid var(--border-md);border-radius:var(--radius-md);font-size:15px;font-family:inherit;background:var(--bg-primary);color:var(--text-primary);transition:border-color .15s,background .15s;outline:none}.answer-input:focus{border-color:var(--blue)}.answer-input.correct{border-color:var(--green)!important;background:var(--bg-success)!important}.answer-input.wrong{border-color:var(--red)!important;background:var(--bg-danger)!important}.answer-unit{font-size:13px;color:var(--text-secondary);min-width:44px}.btn-row{display:flex;gap:8px}.btn{padding:10px 20px;border-radius:var(--radius-md);border:.5px solid var(--border-md);font-size:14px;font-family:inherit;cursor:pointer;background:var(--bg-primary);color:var(--text-primary);display:inline-flex;align-items:center;gap:6px;transition:all .15s}.btn:hover{background:var(--bg-secondary)}.btn:active{transform:scale(.98)}.btn-primary{background:var(--blue);color:#e6f1fb;border-color:var(--blue)}.btn-primary:hover{filter:brightness(1.1);background:var(--blue)}.feedback{border-radius:var(--radius-md);padding:14px 18px;margin-top:1rem;font-size:14px;line-height:1.8;display:none}.feedback.correct{background:var(--bg-success);color:var(--text-success)}.feedback.wrong{background:var(--bg-danger);color:var(--text-danger)}.feedback strong{font-weight:500}.loading{text-align:center;padding:2.5rem 1rem;color:var(--text-secondary);font-size:14px}.spinner{display:inline-block;width:18px;height:18px;border:2px solid var(--border-md);border-top-color:var(--blue);border-radius:50%;animation:spin .7s linear infinite;vertical-align:middle;margin-right:8px}@keyframes spin{to{transform:rotate(360deg)}}.error-msg{color:var(--text-danger)}@media (max-width: 480px){body{padding:1rem .75rem}.stats{gap:6px}.stat{padding:10px 12px}.stat-val{font-size:20px}.problem-card{padding:1.25rem}}.scratchpad{background:var(--bg-primary);border:.5px solid var(--border);border-radius:var(--radius-lg);padding:1rem;margin-top:1rem}.scratchpad-header{display:flex;justify-content:space-between;align-items:flex-start;gap:12px;margin-bottom:10px}.scratchpad-title{font-size:14px;font-weight:500;color:var(--text-primary);display:flex;align-items:center;gap:6px}.scratchpad-title i{color:var(--blue);font-size:18px}.scratchpad-note{font-size:12px;color:var(--text-secondary);margin-top:4px;line-height:1.5}.btn-small{padding:7px 12px;font-size:12px;flex:0 0 auto}.scratch-canvas{width:100%;height:220px;display:block;background:linear-gradient(var(--border) 1px,transparent 1px),linear-gradient(90deg,var(--border) 1px,transparent 1px),var(--bg-primary);background-size:24px 24px;border:.5px solid var(--border-md);border-radius:var(--radius-md);cursor:crosshair;touch-action:none}@media (max-width: 480px){body{padding:1rem .75rem}.header{align-items:flex-start;gap:10px}.header h1{font-size:18px;line-height:1.35}.btn-row{display:grid;grid-template-columns:1fr 1fr}.btn{justify-content:center;padding-left:12px;padding-right:12px}.scratchpad{padding:.85rem}.scratch-canvas{height:260px}}