styles.css

html,
body {
    width: 100%;
    height: 100%;
}

#player {
    background: blue;
    width: 100px;
    height: 50px;
    transition: 0.5s;
}

#board {
    display: flex;
    flex-wrap: wrap;
    width: 50%;
    height: 50%;
    margin: 0 auto;
   
    
}

.square {
    border: 1px solid black;
    width: 33%;
    height: 33%;
    cursor: pointer;
    background: yellow;
    transition: 1s;
    color: yellow;
    position: relative;
}

.flip {
    -moz-transform: rotateY(180deg);
    -o-transform: rotateY(180deg);
    -webkit-transform: rotateY(180deg);
    transform: rotateY(180deg);
    background: red;
    color: #fff!important;
    font-size: 50px;
    text-shadow: 3px 4px 5px black;
}

.content {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translateX(-50%) translateY(-50%);
}

.match{
  -moz-transform: rotateY(180deg);
    -o-transform: rotateY(180deg);
    -webkit-transform: rotateY(180deg);
    transform: rotateY(180deg);
    background: green;
    color: #fff!important;
    font-size: 50px;
    font-weight: 800;
    text-shadow: 3px 4px 5px black;
}



@keyframes win-animation {
    0%   {background-color: chartreuse;}
    25%  {background-color: cadetblue;}
    50%  {background-color: chocolate;}
    100% {background-color: aqua;}
}

/* The element to apply the animation to */
.win {

    background-color: red;
    animation-name: win-animation;
    animation-duration: 4s;
}