.sudoku-board{border-collapse:collapse;margin:20px auto;box-shadow:0 4px 24px #00000026;background:#fff}.sudoku-board td{width:40px;height:40px;text-align:center;border:1px solid #bbb;font-size:1.2em;background:#f7f7fa;transition:background .2s,box-shadow .2s;position:relative}.sudoku-board td.thick-top{border-top:3px solid #4b2e83}.sudoku-board td.thick-left{border-left:3px solid #4b2e83}.sudoku-board td.thick-right{border-right:3px solid #4b2e83}.sudoku-board td.thick-bottom{border-bottom:3px solid #4b2e83}.sudoku-board td.focused-cell{outline:3px solid #4b2e83;box-shadow:0 2px 8px #4c38a026;z-index:1}.sudoku-board td.prefilled{background:#e0e7ff;font-weight:700;color:#4b2e83}.sudoku-board td.error-cell{background:#ffe0e0;animation:shake .2s}.sudoku-board input{width:36px;height:36px;font-size:1.1em;text-align:center;border:none;background:transparent;outline:none}.sudoku-board input.error-input{color:#d00;font-weight:700}@keyframes shake{0%{transform:translate(0)}25%{transform:translate(-2px)}50%{transform:translate(2px)}75%{transform:translate(-2px)}to{transform:translate(0)}}.game-stats{margin:20px auto;padding:10px 20px;background:#eaf6ff;border-radius:8px;box-shadow:0 2px 8px #00000012;display:block;text-align:center}.app{font-family:Segoe UI,Roboto,Arial,sans-serif;background:linear-gradient(120deg,#e0c3fc,#8ec5fc);min-height:100vh;padding:30px 0}h1{text-align:center;color:#4b2e83;margin-bottom:20px;letter-spacing:2px}button{display:block;margin:20px auto;padding:10px 24px;font-size:1em;background:#4b2e83;color:#fff;border:none;border-radius:6px;cursor:pointer;box-shadow:0 2px 8px #00000014;transition:background .2s}button:hover{background:#6c47b6}