.container{
    display: grid;
    place-items: center;
    background: linear-gradient(135deg, #010024, #050f2c);
    min-height: 100vh;
}
.container h1{
    text-align: center;
    font-family:'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    font-size: 3.5rem;
    font-weight: 500;
    color: #90f5f9;
}
.cards{
  display: grid;
  grid-template-columns: repeat(4, 100px);
  grid-gap: 15px;
  margin: 10px 10px;
}
.card{
  height: 120px;
  width: 100px;
  background: #90f5f9;
  border: 1px solid #90f5f7;
  box-shadow: 0 0  80px #49f0f9;
  border-radius: 10px;
  cursor: pointer;
  transition: all .3s ease;     
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
  overflow: hidden;
}
.card:hover{ transform: scale(1.03);
background:#2df4fa;
box-shadow:  0 0 80px;}
.card img{
  width: 100%;
  height: 100%;
  transition: all .3s ease;
  opacity: 0;
  object-fit: cover;
}
.card.clicked{
  background-image: none;
  background-color: #daeafd;
}
.card.clicked img{
  opacity: 1;
}
.card.checked {
  background-color: #35fb7e;
  transform: rotateY(180deg);
}
.card.checked::after {
  content: "✔";
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%) rotateY(180deg);
  color: #03c7a0;
  font-size: 2rem;
  font-weight: bold;
  text-shadow: 0 0 8px #00ffcc, 0 0 15px #00ffcc, 0 0 25px #00ffcc;
}
@keyframes shake {
  0% { transform: translateX(0); }
  25% { transform: translateX(-8px); }
  50% { transform: translateX(8px); }
  75% { transform: translateX(-6px); }
  100% { transform: translateX(0); }
}
.card.shake img{
  opacity: 0.5;
}
.card.shake {
  animation: shake 0.5s;
  box-shadow: 0 0 80px;
  transform:rotateY(360deg);
  background-color: red;
}
.card.shake::after{
  content: "X";
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%) rotateY(180deg);
  color: #f30606;
  font-size: 2rem;
  font-weight: bold;
  text-shadow: 0 0 8px #ff1100, 0 0 15px #ff1100, 0 0 25px #ff1100;
} 
@media(max-width:500px){
  .cards{
    grid-template-columns: repeat(4, 70px);
    grid-gap: 10px;
    margin: 10px 5px;
  }
  .card{
    height: 90px;
    width: 70px;
  }
  .container h1{
    font-size: 2.5rem;
  }
}