:root{--primary-color:#0070f3}*{box-sizing:border-box}body{font-family:sans-serif;margin:20px;padding:0}.sudoku-container{display:flex;flex-direction:column;align-items:center;gap:20px}.board{border:2px solid #333;padding:4px}.board-row{display:flex;gap:1px}.square{width:30px;height:30px;font-size:20px;text-align:center;border:2px solid #ccc;margin:1px;background-color:white}.square.error{border-color:#ff4444;background-color:#ffe6e6}.controls{display:flex;gap:10px;margin-bottom:20px}.button{background-color:#0070f3}.button,.button2{padding:8px 16px;color:white;border:none;border-radius:4px;cursor:pointer;transition:opacity .2s}.button2{background-color:rgb(92,77,187)}.button:hover{opacity:.8}.message{padding:10px;margin:10px 0;border-radius:4px;text-align:center;font-weight:700}.message.success{background-color:#e6ffe6;color:#2a8a2a;border:1px solid #2a8a2a}.message.error{background-color:#ffe6e6;color:#ee5252;border:1px solid #ff4444}