body{background:#f4f6f8;justify-content:center;margin:0;font-family:Arial,sans-serif;display:flex}#app{flex-direction:column;align-items:center;padding:30px;display:flex}h1{margin-bottom:20px}.difficulty-selector{gap:12px;margin-bottom:25px;display:flex}.difficulty-selector input{display:none}.difficulty-selector label{cursor:pointer;background-color:#e5e7eb;border-radius:10px;align-items:center;gap:6px;padding:10px 16px;font-weight:700;transition:all .2s;display:flex}.difficulty-selector label:hover{transform:scale(1.05);box-shadow:0 3px 8px #00000026}.difficulty-selector input:checked+label{color:#fff;background-color:#22c55e}.easy:before{content:"😎"}.medium:before{content:"😐"}.hard:before{content:"😈"}.expert:before{content:"💀"}#board{background:#1e40af;border-radius:12px;grid-template-columns:repeat(7,1fr);gap:6px;width:min(95vw,420px);margin:20px 0;padding:12px;display:grid;box-shadow:0 8px 20px #00000040}.cell{aspect-ratio:1;background:#e5e7eb;border-radius:50%;width:100%;transition:transform .2s;box-shadow:inset 0 4px 6px #0003}.cell:hover{transform:scale(1.05)}.cell.player{background:radial-gradient(circle at 30% 30%,#ff4d4d,#b91c1c)}.cell.ai{background:radial-gradient(circle at 30% 30%,#fde047,#ca8a04)}.fall{animation:.3s fall}@keyframes fall{0%{transform:translateY(-200px)}to{transform:translateY(0)}}#status{min-height:30px;margin-top:10px;font-size:1.4rem;font-weight:700}#restart{color:#fff;cursor:pointer;background:#3b82f6;border:none;border-radius:8px;margin-top:20px;padding:10px 20px;font-size:1rem;font-weight:700;transition:all .2s}#restart:hover{background:#2563eb;transform:scale(1.05)}@media (width<=480px){.difficulty-selector{gap:8px}.difficulty-selector label{padding:8px 12px;font-size:.85rem}#board{gap:4px;padding:8px}}