:root{--primary-color:#2f80ed;--secondary-color:#56ccf2;--accent-color:#f2c94c;--text-dark:#333;--text-light:#fff;--bg-light:#f4f7f6;--bg-white:#fff;--danger-color:#eb5757;--success-color:#27ae60;--font-main:"Segoe UI", Tahoma, Geneva, Verdana, sans-serif;--spacing-unit:1rem;--shadow-card:0 4px 6px #0000001a;--shadow-hover:0 10px 15px #0000001a}*{box-sizing:border-box;margin:0;padding:0}body{font-family:var(--font-main);background-color:var(--bg-light);color:var(--text-dark);flex-direction:column;min-height:100vh;line-height:1.6;display:flex}h1,h2,h3,h4,h5,h6{margin-bottom:.5em;font-weight:600}h1{font-size:2.5rem}h2{font-size:2rem}h3{font-size:1.75rem}a{color:var(--primary-color);text-decoration:none}.container{flex:1;width:100%;max-width:1200px;margin:0 auto;padding:2rem}.text-center{text-align:center}.mt-1{margin-top:1rem}.mb-1{margin-bottom:1rem}.mt-2{margin-top:2rem}.mb-2{margin-bottom:2rem}.btn{background:linear-gradient(135deg, var(--secondary-color) 0%, var(--primary-color) 100%);color:var(--text-light);text-transform:uppercase;letter-spacing:1px;cursor:pointer;border:none;border-radius:50px;padding:.8rem 1.5rem;font-size:1rem;font-weight:700;transition:transform .2s,box-shadow .2s;display:inline-block}.btn:hover{background:linear-gradient(135deg, var(--secondary-color) 20%, var(--primary-color) 100%);transform:translateY(-3px);box-shadow:0 5px 15px #2f80ed66}.btn-secondary{border:2px solid var(--primary-color);color:var(--primary-color);background:0 0}.btn-secondary:hover{background:var(--primary-color);color:var(--text-light)}.card{background:var(--bg-white);box-shadow:var(--shadow-card);border-radius:12px;padding:2rem;transition:transform .3s,box-shadow .3s}.card:hover{box-shadow:var(--shadow-hover);transform:translateY(-5px)}.navbar{background:linear-gradient(135deg, var(--secondary-color) 0%, var(--primary-color) 100%);z-index:1000;justify-content:space-between;align-items:center;padding:.8rem 2rem;display:flex;position:sticky;top:0;box-shadow:0 2px 10px #0000001a}.nav-brand{color:var(--text-light);font-size:1.5rem;font-weight:700}.nav-links{gap:1.5rem;list-style:none;display:flex}.nav-links li a{color:var(--text-light);border-radius:20px;padding:.5rem 1rem;font-size:1rem;transition:background .3s;display:block}.nav-links li a:hover{background:#fff3}.nav-links li a.active{background:#ffffff4d;font-weight:700}@media (width<=768px){.container{padding:1rem}h1{font-size:2rem}.navbar{border-top:1px solid #ffffff1a;justify-content:center;width:100%;padding:.5rem 1rem;position:fixed;top:auto;bottom:0}.nav-brand{display:none}.nav-links{justify-content:space-between;gap:0;width:100%}.nav-links li a{text-align:center;flex-direction:column;align-items:center;padding:.5rem;font-size:.8rem;display:flex}body{padding-bottom:70px}}#root,.app-shell{min-height:100vh}.page-shell{flex-direction:column;gap:2rem;display:flex}.page-intro{text-align:center;max-width:720px;margin:0 auto 1.5rem}.hero{text-align:center;background:radial-gradient(circle,#56ccf21f 0%,#fff0 72%);flex-direction:column;justify-content:center;align-items:center;min-height:80vh;display:flex}.hero-icon{background:linear-gradient(135deg, var(--secondary-color), var(--primary-color));width:6rem;height:6rem;color:var(--text-light);border-radius:50%;place-items:center;margin-bottom:1.25rem;font-size:2.4rem;font-weight:700;display:grid;box-shadow:0 16px 30px #2f80ed33}.hero-copy{max-width:640px;margin-bottom:1.5rem;font-size:1.15rem}.hero-actions{flex-wrap:wrap;justify-content:center;gap:1rem;display:flex}.features{grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:1.5rem;width:100%;margin-top:3rem;display:grid}.feature-card{background:var(--bg-white);text-align:left;box-shadow:var(--shadow-card);border-radius:12px;padding:1.5rem}.feature-card h3{color:var(--primary-color)}.selection-grid{grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:2rem;display:grid}.game-card{flex-direction:column;justify-content:space-between;gap:1rem;display:flex}.game-author{color:#666;margin-bottom:.75rem;font-size:.95rem;font-style:italic}.difficulty-badge{border-radius:999px;margin-bottom:1rem;padding:.3rem .8rem;font-size:.85rem;font-weight:700;display:inline-block}.badge-easy{color:var(--success-color);border:1px solid var(--success-color);background-color:#e7faf0}.badge-normal{color:var(--primary-color);border:1px solid var(--primary-color);background-color:#eef6ff}.rules-content,.scores-container,.auth-container,.game-board-card{background:var(--bg-white);box-shadow:var(--shadow-card);border-radius:14px}.rules-content{max-width:860px;margin:0 auto;padding:2.5rem}.rules-list{counter-reset:rule-counter;margin:2rem 0;list-style:none}.rules-list li{margin-bottom:1.5rem;padding-left:3.25rem;position:relative}.rules-list li:before{counter-increment:rule-counter;content:counter(rule-counter);background:var(--primary-color);width:2rem;height:2rem;color:var(--text-light);border-radius:50%;place-items:center;font-weight:700;display:grid;position:absolute;top:0;left:0}.credits{text-align:center;border-top:1px solid #e8ebf0;margin-top:2.5rem;padding-top:2rem}.credits-links{flex-wrap:wrap;justify-content:center;gap:1rem;margin-top:1rem;display:flex}.scores-container{padding:1.5rem;overflow-x:auto}table{border-collapse:collapse;width:100%}th,td{text-align:left;border-bottom:1px solid #edf0f5;padding:1rem}th{background:var(--primary-color);color:var(--text-light);text-transform:uppercase;letter-spacing:.04em;font-size:.85rem}tr:nth-child(2n){background:#f8fafc}.auth-container{width:100%;max-width:420px;margin:0 auto;padding:2rem}.form-group{margin-bottom:1.25rem}.form-group label{margin-bottom:.5rem;font-weight:600;display:block}.form-group input{border:1px solid #d7dce5;border-radius:8px;width:100%;padding:.85rem 1rem;font-size:1rem}.form-group input:focus{border-color:var(--primary-color);outline:none;box-shadow:0 0 0 3px #2f80ed1f}.auth-button{width:100%}.auth-footer{text-align:center;color:#5f6b7a;margin-top:1rem}.game-page{flex-direction:column;gap:1.5rem;display:flex}.game-header{flex-wrap:wrap;justify-content:space-between;align-items:flex-start;gap:1rem;display:flex}.game-subtitle{color:#5f6b7a;max-width:560px}.game-header-side{flex-direction:column;align-items:flex-end;gap:.75rem;display:flex}.timer{color:var(--text-light);text-align:center;background:#18212f;border-radius:10px;min-width:6.5rem;padding:.55rem 1rem;font-family:Courier New,Courier,monospace;font-size:1.5rem}.status-banner{color:var(--primary-color);background:#eef6ff;border-radius:999px;padding:.55rem .9rem;font-size:.92rem}.status-banner.success{color:var(--success-color);background:#e7faf0}.game-board-card{padding:1.25rem}.sudoku-grid{background:#1f2937;border:3px solid #1f2937;gap:1px;width:min(100%,640px);margin:0 auto;display:grid}.sudoku-grid-easy{max-width:540px}.sudoku-cell{aspect-ratio:1;text-align:center;width:100%;color:var(--primary-color);cursor:pointer;background:#fff;border:1px solid #dbe2ea;font-size:1.35rem;font-weight:600;transition:background-color .2s,border-color .2s,transform .15s}.sudoku-cell:disabled{opacity:1;-webkit-text-fill-color:currentColor}.sudoku-cell:hover{background:#f5fbff}.sudoku-cell:focus{outline:none}.sudoku-cell.selected{border-color:var(--primary-color);background:#e8f3ff}.sudoku-cell.fixed{color:#27303f;cursor:default;background:#f2f4f7}.sudoku-cell.hint{background:#fffbe6;box-shadow:inset 0 0 0 3px #f2c94c}.sudoku-cell.invalid{border:2px solid var(--danger-color);color:var(--danger-color);background:#fff5f5}.sudoku-cell.subgrid-right{border-right:3px solid #1f2937}.sudoku-cell.subgrid-bottom{border-bottom:3px solid #1f2937}.game-controls{flex-wrap:wrap;justify-content:center;gap:1rem;display:flex}@media (width<=768px){.rules-content,.scores-container,.auth-container,.game-board-card{padding:1.2rem}.game-header-side{align-items:flex-start}}@media (width<=540px){.hero{min-height:auto;padding-top:1rem}.hero-copy,.sudoku-cell{font-size:1rem}th,td{padding:.7rem .5rem;font-size:.85rem}}