.layout{min-height:100vh;display:flex;flex-direction:column}.header{background:var(--surface);border-bottom:1px solid var(--border);padding:1rem 0}.header .container{display:flex;justify-content:space-between;align-items:center}.logo{font-size:1.5rem;font-weight:700;color:var(--primary);text-decoration:none}.nav{display:flex;gap:1rem}.nav-link{color:var(--text-muted);text-decoration:none;padding:.5rem 1rem;border-radius:6px;transition:all .2s}.nav-link:hover{color:var(--primary);background:var(--background)}.nav-link.active{color:var(--primary);background:var(--background);font-weight:500}.main{flex:1;padding:2rem 0}.footer{background:var(--surface);border-top:1px solid var(--border);padding:2rem 0;text-align:center;color:var(--text-muted)}@media (max-width: 768px){.header .container{flex-direction:column;gap:1rem}.nav{flex-wrap:wrap;justify-content:center}}.home{text-align:center}.hero{margin-bottom:3rem}.hero h1{font-size:3rem;font-weight:700;color:var(--primary);margin-bottom:1rem}.tagline{font-size:1.2rem;color:var(--text-muted);margin-bottom:0}.tools-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:2rem;margin-top:2rem}.tool-card{background:var(--surface);border-radius:12px;padding:2rem;text-align:center;box-shadow:var(--shadow);transition:transform .2s,box-shadow .2s;border:1px solid var(--border)}.tool-card:hover{transform:translateY(-4px);box-shadow:var(--shadow-lg)}.tool-icon{font-size:3rem;margin-bottom:1rem}.tool-card h3{font-size:1.5rem;margin-bottom:1rem;color:var(--text)}.tool-card p{color:var(--text-muted);margin-bottom:2rem}@media (max-width: 768px){.hero h1{font-size:2rem}.tools-grid{grid-template-columns:1fr}}.sudoku-grid{display:grid;grid-template-columns:repeat(9,1fr);gap:2px;max-width:450px;margin:0 auto;border:3px solid #333;background:#333}.sudoku-cell{width:50px;height:50px;border:1px solid #ccc;display:flex;align-items:center;justify-content:center;font-size:1.2rem;font-weight:700;background:white;text-align:center;outline:none;transition:all .2s}.sudoku-cell:focus{background:#fef3c7;border-color:#f59e0b}.sudoku-cell.related{background:#dbeafe}.sudoku-cell.same-value{background:#fecaca}.sudoku-cell.original{background:#f3f4f6;color:#6b7280}.sudoku-cell.solved{background:#dcfce7;color:#166534}.sudoku-cell.current{background:#fef3c7;border-color:#f59e0b;box-shadow:0 0 0 2px #f59e0b}.sudoku-cell:nth-child(3n){border-right:2px solid #333}.sudoku-cell:nth-child(n+19):nth-child(-n+27),.sudoku-cell:nth-child(n+46):nth-child(-n+54){border-bottom:2px solid #333}.sudoku-cell:disabled{cursor:not-allowed;opacity:.7}@media (max-width: 768px){.sudoku-grid{max-width:100%}.sudoku-cell{width:40px;height:40px;font-size:1rem}}.sudoku-page{max-width:800px;margin:0 auto}.sudoku-header{text-align:center;margin-bottom:2rem}.sudoku-header h1{font-size:2.5rem;color:var(--primary);margin-bottom:.5rem}.sudoku-header p{color:var(--text-muted);font-size:1.1rem}.sudoku-container{display:flex;flex-direction:column;align-items:center;gap:2rem}.controls{display:flex;gap:1rem;flex-wrap:wrap;justify-content:center}.error-message{background:#fee2e2;color:#dc2626;padding:1rem;border-radius:8px;border:1px solid #fecaca;text-align:center}.success-message{background:#dcfce7;color:#166534;padding:1rem;border-radius:8px;border:1px solid #bbf7d0;text-align:center}@media (max-width: 768px){.controls{flex-direction:column;align-items:center}.controls .btn{width:200px}}.text-tools-page{max-width:800px;margin:0 auto;text-align:center}.text-tools-header{margin-bottom:2rem}.text-tools-header h1{font-size:2.5rem;color:var(--primary);margin-bottom:.5rem}.text-tools-header p{color:var(--text-muted);font-size:1.1rem}.calculator-page{max-width:800px;margin:0 auto;text-align:center}.calculator-header{margin-bottom:2rem}.calculator-header h1{font-size:2.5rem;color:var(--primary);margin-bottom:.5rem}.calculator-header p{color:var(--text-muted);font-size:1.1rem}.coming-soon{background:var(--surface);padding:3rem;border-radius:12px;border:1px solid var(--border)}.coming-soon h2{color:var(--text);margin-bottom:1rem}.coming-soon p{color:var(--text-muted)}:root{--primary: #3b82f6;--primary-dark: #2563eb;--secondary: #64748b;--success: #10b981;--warning: #f59e0b;--error: #ef4444;--background: #f8fafc;--surface: #ffffff;--text: #1e293b;--text-muted: #64748b;--border: #e2e8f0;--shadow: 0 1px 3px 0 rgba(0, 0, 0, .1);--shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, .1)}*{margin:0;padding:0;box-sizing:border-box}body{font-family:Segoe UI,Tahoma,Geneva,Verdana,sans-serif;background:var(--background);color:var(--text);line-height:1.6}.container{max-width:1200px;margin:0 auto;padding:0 1rem}.btn{display:inline-block;padding:.75rem 1.5rem;border-radius:8px;text-decoration:none;font-weight:500;transition:all .2s;border:none;cursor:pointer;font-size:1rem}.btn-primary{background:var(--primary);color:#fff}.btn-primary:hover{background:var(--primary-dark);transform:translateY(-1px)}.btn-secondary{background:var(--secondary);color:#fff}.btn-secondary:hover{background:#475569;transform:translateY(-1px)}.btn:disabled{opacity:.6;cursor:not-allowed;transform:none}@media (max-width: 768px){.container{padding:0 .5rem}}