*{margin:0;padding:0;box-sizing:border-box}html,body{height:100%;width:100%;display:flex;justify-content:center}.app{display:flex;flex-direction:column;align-items:center;justify-content:flex-start;min-height:100vh;padding:40px 0}h1{margin-bottom:2rem;color:#000;background:#fff;padding:1rem 2rem;border-radius:8px;font-size:2rem;font-weight:700}.cards-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:20px;transition:opacity .3s ease;opacity:1}.app.game-won .cards-grid{opacity:.3;pointer-events:none}.overlay{position:fixed;top:0;left:0;width:100%;height:100%;background-color:#0009;-webkit-backdrop-filter:blur(4px);backdrop-filter:blur(4px);display:flex;justify-content:center;align-items:center;z-index:1000}.overlay-content{background:#fff;padding:2rem 3rem;border-radius:12px;text-align:center;box-shadow:0 0 20px #fff3}.overlay-content h2{margin-bottom:1rem;font-size:2rem;color:#333}.overlay-content button{background-color:#4caf50;color:#fff;padding:.8rem 1.5rem;border:none;border-radius:8px;font-size:1rem;cursor:pointer;transition:background-color .3s ease}.overlay-content button:hover{background-color:#45a049}.card{perspective:1000px;cursor:pointer}.card-inner{width:150px;height:150px;position:relative;transform-style:preserve-3d;transition:transform .6s}.card.flipped .card-inner{transform:rotateY(180deg)}.card-front,.card-back{position:absolute;width:100%;height:100%;backface-visibility:hidden;border-radius:12px}.card-front{background-color:#d3d3d3}.card-back{transform:rotateY(180deg)}.card:not(.flipped):hover .card-front{background-color:#9dcadf}.card-img{width:150px;height:150px;border-radius:12px}