.footer,
.footer a {
    color: #777;
}
.card,
body,
html {
    position: relative;
}
.card,
.card:before {
    width: 40px;
    height: 40px;
}
* {
    box-sizing: border-box;
}
body,
html {
    font-family: sans-serif;
    margin: 0;
    padding: 0;
    min-height: 100vh;
}
.container {
    display: flex;
    min-height: 100vh;
    justify-content: space-between;
    flex-direction: column;
}
.container .content {
    flex-grow: 1;
}
.footer {
    text-align: center;
    padding: 10px 0;
    background: #f0f0f0;
}
#credits,
#credits a {
    color: #ccc;
}
#game {
    max-width: 298px;
    margin: 2em auto 0;
}
#game h4 {
    margin-top: 0;
}
#board {
    padding: 0.5em;
    border: 1px solid #f0f0f0;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(40px, 40px));
    grid-gap: 0.5em;
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.1);
}
#credits {
    margin-top: 10px;
    text-align: center;
    font-size: 85%;
}
.card.found,
.card.not-match {
    color: #fff;
}
.card {
    display: flex;
    align-items: center;
    justify-content: center;
    transform-style: preserve-3d;
    transform: rotateY(180deg);
    transition: all 0.3s ease-in-out, color 0s linear;
}
.card i {
    visibility: hidden;
    opacity: 0;
}
.card.active,
.card.found {
    transform: rotateY(0);
}
.card.active i,
.card.found i {
    visibility: visible;
    opacity: 1;
}
.card.found:before {
    background-color: #7ee8b7;
}
.card.not-match:before {
    background-color: tomato;
}
.card:before {
    content: "";
    display: block;
    position: absolute;
    background: #f0f0f0;
    transform-origin: 50% 50%;
    transform: rotateY(0);
    z-index: -1;
}
.panel {
    display: flex;
    justify-content: space-between;
    margin-bottom: 1em;
}
.animated {
    -webkit-animation-duration: 1s;
    animation-duration: 1s;
    -webkit-animation-fill-mode: both;
    animation-fill-mode: both;
}
@keyframes shake {
    from,
    to {
        -webkit-transform: translate3d(0, 0, 0);
        transform: translate3d(0, 0, 0);
    }
    10%,
    30%,
    50%,
    70%,
    90% {
        -webkit-transform: translate3d(-10px, 0, 0);
        transform: translate3d(-10px, 0, 0);
    }
    20%,
    40%,
    60%,
    80% {
        -webkit-transform: translate3d(10px, 0, 0);
        transform: translate3d(10px, 0, 0);
    }
}
.shake {
    -webkit-animation-name: shake;
    animation-name: shake;
}
@keyframes tada {
    from,
    to {
        -webkit-transform: scale3d(1, 1, 1);
        transform: scale3d(1, 1, 1);
    }
    10%,
    20% {
        -webkit-transform: scale3d(0.9, 0.9, 0.9) rotate3d(0, 0, 1, -3deg);
        transform: scale3d(0.9, 0.9, 0.9) rotate3d(0, 0, 1, -3deg);
    }
    30%,
    50%,
    70%,
    90% {
        -webkit-transform: scale3d(1.1, 1.1, 1.1) rotate3d(0, 0, 1, 3deg);
        transform: scale3d(1.1, 1.1, 1.1) rotate3d(0, 0, 1, 3deg);
    }
    40%,
    60%,
    80% {
        -webkit-transform: scale3d(1.1, 1.1, 1.1) rotate3d(0, 0, 1, -3deg);
        transform: scale3d(1.1, 1.1, 1.1) rotate3d(0, 0, 1, -3deg);
    }
}
.tada {
    -webkit-animation-name: tada;
    animation-name: tada;
}