.sudoku-card{max-width:600px;margin:0 auto}.timer-display{text-align:center;margin-bottom:1rem;font-size:1.5rem;font-weight:600;color:#3498db}.timer-icon{margin-right:.5rem}.difficulty-selector{display:flex;flex-wrap:wrap;justify-content:center;gap:.5rem;margin-bottom:1.5rem}.btn-difficulty{padding:.5rem 1rem;border:2px solid #3498db;background:var(--bi-surface);color:#3498db;border-radius:8px;font-weight:500;transition:all .3s ease}.btn-difficulty:hover,.btn-difficulty.active{background:#3498db;color:#fff}.custom-difficulty{display:flex;gap:.5rem;align-items:center}.custom-difficulty input{width:80px;text-align:center}.sudoku-board{width:100%;max-width:450px;margin:0 auto 1.5rem;aspect-ratio:1;display:grid;grid-template-columns:repeat(9,1fr);grid-template-rows:repeat(9,1fr);border:3px solid #2c3e50;background:var(--bi-surface)}.sudoku-cell{border:1px solid #bdc3c7;display:flex;align-items:center;justify-content:center;font-size:1.5rem;font-weight:600;cursor:pointer;transition:all .2s ease;user-select:none}.sudoku-cell:hover{background:#ecf0f1}.sudoku-cell.selected{background:#3498db;color:#fff}.sudoku-cell.highlighted{background:#e8f4f8}.sudoku-cell.same-number{background:#d5e8d4}.sudoku-cell.fixed{color:var(--bi-text);background:var(--bi-surface-2);font-weight:700}.sudoku-cell.editable{color:#ff922b}.sudoku-cell.error{background:#ffebee;color:#e74c3c}.sudoku-cell:nth-child(3n){border-right:2px solid #2c3e50}.sudoku-cell:nth-child(9n){border-right:none}.sudoku-cell:nth-child(n+19):nth-child(-n+27),.sudoku-cell:nth-child(n+46):nth-child(-n+54){border-bottom:2px solid #2c3e50}.game-controls{display:flex;flex-wrap:wrap;justify-content:center;gap:.75rem;margin-bottom:1.5rem}.number-pad{margin-bottom:1.5rem}.number-row{display:flex;justify-content:center;gap:.5rem;margin-bottom:.5rem}.num-btn{width:50px;height:50px;border:2px solid #3498db;background:var(--bi-surface);color:#3498db;border-radius:8px;font-size:1.25rem;font-weight:600;transition:all .2s ease}.num-btn:hover,.num-btn:active{background:#3498db;color:#fff}.num-btn.btn-clear{border-color:#e74c3c;color:#e74c3c}.num-btn.btn-clear:hover,.num-btn.btn-clear:active{background:#e74c3c;color:#fff}.game-instructions{background:var(--bi-surface-2);padding:1.5rem;border-radius:12px}.game-instructions h5{color:var(--bi-text);margin-bottom:1rem;text-align:center}.game-instructions ul{color:#7f8c8d;padding-left:1.5rem;margin:0}.game-instructions li{margin-bottom:.5rem}.print-area{display:none}.result-message{font-size:1.25rem;color:var(--bi-text);margin-bottom:.5rem}.result-time{font-size:1rem;color:#7f8c8d}@media print{body *{visibility:hidden}.print-area,.print-area *{visibility:visible}.print-area{display:block;position:absolute;left:0;top:0;width:100%}.print-sudoku{page-break-inside:avoid;margin-bottom:2rem}}@media (max-width: 576px){.sudoku-card{padding:1rem}.game-title{font-size:1.75rem}.sudoku-cell{font-size:1.25rem}.difficulty-selector{flex-direction:column;align-items:center}.custom-difficulty{width:100%;justify-content:center}.game-controls{flex-direction:column}.game-controls .btn{width:100%}}html[data-theme=dark] .sudoku-board{border-color:#64748b}html[data-theme=dark] .sudoku-cell{border-color:#475569}html[data-theme=dark] .sudoku-cell:nth-child(3n){border-right-color:#64748b}html[data-theme=dark] .sudoku-cell:nth-child(n+19):nth-child(-n+27),html[data-theme=dark] .sudoku-cell:nth-child(n+46):nth-child(-n+54){border-bottom-color:#64748b}html[data-theme=dark] .sudoku-cell:hover{background:#334155}html[data-theme=dark] .sudoku-cell.highlighted{background:#1e3a5f}html[data-theme=dark] .sudoku-cell.same-number{background:#1e3a2f}html[data-theme=dark] .sudoku-cell.error{background:#4a1d22;color:#ff8793}