main {
  width: 320px;
  margin: 5px auto;
}

/* game */
#display {
  width: 320px;
  display: flex;
  flex-wrap: wrap;
}
h3 {
  margin: 0;
  width: 160px;
}
#board {
  display: flex;
  width: 320px;
  flex-wrap: wrap;
}
.start {
  height: 320px;
  background: rgb(102, 204, 153);
  color: white;
  border-radius: 5px;
}
.start:hover {
  opacity: 0.5;
}
#startBtn {
  width: 320px;
  font-size: 24px;
  font-weight: bold;
  text-align: center;
  line-height: 280px;
  cursor: pointer;
}
.cell {
  width: 60px;
  height: 60px;
  margin: 2px;
  border-radius: 3px;
}
.correctCell {
  border: solid 4px red;
  width: 52px;
  height: 52px;
}
.heart::before {
  font-family: "Material Icons";
  content: "\e87d";
}
#end {
  display: none;
  width: 320px;
  text-align: center;
}
#end h3 {
  width: 320px;
  text-align: center;
}
#end p {
  cursor: pointer;
  padding: 3px;
  border: solid 1px black;
  border-radius: 4px;
  background: black;
  color: white;
}
#end p:hover {
  background: white;
  color: black;
}
.heart2 {
  text-align: center;
  line-height: 60px;
  font-size: 48px;
  font-weight: bold;
}
.heart2::before {
  font-family: "Material Icons";
  content: "\e87e";
  animation: fadein 2s infinite;
}
@keyframes fadein {
  0% {
    opacity: 0;
  }
  50% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}