:root{--primary: #3b82f6;--primary-dark: #2563eb;--bg-app: #f8fafc;--bg-panel: #ffffff;--text-main: #1e293b;--text-muted: #64748b;--border: #e2e8f0;--border-thick: #334155;--cell-size: clamp(40px, 13vw, 56px);--cell-bg: #ffffff;--cell-selected: #bfdbfe;--cell-highlight: #eff6ff;--cell-error: #fecaca;--cell-flash: #86efac;--shadow: 0 4px 6px -1px rgb(0 0 0 / .1), 0 2px 4px -2px rgb(0 0 0 / .1);--radius: 12px}*{box-sizing:border-box}body{margin:0;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;background-color:var(--bg-app);color:var(--text-main);-webkit-tap-highlight-color:transparent}button{cursor:pointer;border:none;font-family:inherit;transition:all .15s ease}button:active{transform:scale(.98)}#root{min-height:100vh;display:flex;flex-direction:column}.container{max-width:500px;margin:0 auto;padding:1rem;width:100%;display:flex;flex-direction:column;align-items:center;gap:1.5rem;flex:1}.header{width:100%;display:flex;justify-content:space-between;align-items:center;margin-bottom:.5rem}.title-group{display:flex;flex-direction:column}.title{font-size:1.5rem;font-weight:800;line-height:1.2;color:var(--text-main)}.subtitle{font-size:.875rem;color:var(--text-muted);font-weight:500}.stats-pill{background:var(--bg-panel);padding:.5rem 1rem;border-radius:20px;box-shadow:var(--shadow);display:flex;flex-direction:column;align-items:flex-end;border:1px solid var(--border)}.timer{font-family:monospace;font-size:1.25rem;font-weight:700;color:var(--primary-dark)}.difficulty-badge{font-size:.7rem;text-transform:uppercase;letter-spacing:.05em;font-weight:700;color:var(--text-muted)}.board-container{background:var(--bg-panel);padding:.5rem;border-radius:var(--radius);box-shadow:var(--shadow)}.sudoku-grid{display:grid;grid-template-columns:repeat(6,1fr);width:fit-content;border:2px solid var(--border-thick);background-color:var(--border-thick);gap:1px}.cell{width:var(--cell-size);height:var(--cell-size);background-color:var(--cell-bg);display:flex;align-items:center;justify-content:center;font-size:1.5rem;font-weight:600;cursor:pointer;-webkit-user-select:none;user-select:none;position:relative;transition:background-color .1s}.cell.thick-right{border-right:2px solid var(--border-thick)}.cell.thick-bottom{border-bottom:2px solid var(--border-thick)}.cell.selected{background-color:var(--cell-selected)!important}.cell.highlighted{background-color:var(--cell-highlight)}.cell.error{background-color:var(--cell-error)!important;color:#991b1b}.cell.flash{background-color:var(--cell-flash)!important;transition:background-color .4s ease-out}.val-initial{color:var(--text-main)}.val-input{color:var(--primary)}.notes-grid{display:grid;grid-template-columns:repeat(3,1fr);width:100%;height:100%}.note-num{font-size:.6rem;color:var(--text-muted);display:flex;align-items:center;justify-content:center}.controls-row{display:flex;width:100%;gap:.5rem;justify-content:center}.control-btn{flex:1;padding:.75rem .25rem;border-radius:8px;background:var(--bg-panel);border:1px solid var(--border);color:var(--text-muted);font-weight:600;font-size:.8rem;display:flex;flex-direction:column;align-items:center;gap:2px;box-shadow:0 1px 2px #0000000d}.control-btn.active{background:var(--primary);color:#fff;border-color:var(--primary-dark)}.control-btn:hover:not(.active){background:#f1f5f9}.numpad{width:100%;display:grid;grid-template-columns:repeat(6,1fr);gap:.5rem}.num-btn{aspect-ratio:1;background:#fff;border-radius:8px;font-size:1.5rem;font-weight:700;color:var(--primary);box-shadow:0 2px 0 var(--border);border:1px solid var(--border)}.num-btn:active{box-shadow:none;transform:translateY(2px)}.action-btn{grid-column:span 3;padding:1rem;border-radius:8px;font-weight:700;text-transform:uppercase;font-size:.9rem;letter-spacing:.05em}.btn-erase{background:#fee2e2;color:#ef4444}.btn-undo{background:#e2e8f0;color:#475569}.modal-overlay{position:fixed;top:0;right:0;bottom:0;left:0;background:#00000080;display:flex;align-items:center;justify-content:center;-webkit-backdrop-filter:blur(2px);backdrop-filter:blur(2px);z-index:50;animation:fadeIn .2s ease-out}.modal-content{background:#fff;padding:2rem;border-radius:1rem;text-align:center;max-width:90%;width:320px;box-shadow:0 20px 25px -5px #0000001a;animation:zoomIn .2s ease-out}.modal-title{font-size:2rem;margin:0 0 1rem}.modal-btn{width:100%;padding:1rem;background:var(--primary);color:#fff;font-weight:700;border-radius:.75rem;margin-top:1rem;font-size:1rem}.home-screen{display:flex;flex-direction:column;align-items:center;justify-content:center;min-height:100vh;gap:2rem;padding:2rem}.home-title{font-size:3rem;font-weight:900;text-align:center;line-height:1;color:var(--text-main)}.home-title span{color:var(--primary)}.diff-btn{width:240px;padding:1rem;font-size:1.1rem;font-weight:700;background:#fff;border:2px solid var(--border);border-radius:1rem;color:var(--text-main);box-shadow:var(--shadow)}.diff-btn:hover{border-color:var(--primary);color:var(--primary)}@keyframes fadeIn{0%{opacity:0}to{opacity:1}}@keyframes zoomIn{0%{opacity:0;transform:scale(.9)}to{opacity:1;transform:scale(1)}}