@import url('https://fonts.googleapis.com/css2?family=Roboto:ital,wght@0,100;0,300;0,400;0,500;0,700;0,900;1,100;1,300;1,400;1,500;1,700;1,900&display=swap');
* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}

body {
    height: 100vh;
    display: flex;
    flex-direction: column;
    background-color: #000000;
    text-align: left;
    top: 0 auto;
    width: 100%;
    color: #ffff;
    font-family: 'Roboto';
}

.txtalign {
    font-family: Open Sans;
    font-size: 20px;
    font-weight: 300;
    color: #ffffff;
    text-align: center;
}

.memory-game {
    height: 640px;
    width: 640px;
    margin: 0 auto;
    display: flex;
    flex-wrap: wrap;
    perspective: 1000px;
    /* perspectiva do usuário */
}

.card {
    height: calc( 33.333% - 10px);
    width: calc(25% - 10px);
    margin: 0 auto;
    position: relative;
    box-shadow: 1px 1px 1px rgba(0, 0, 0, .3);
    cursor: pointer;
    transform: scale(1);
    transform-style: preserve-3d;
    /* perspectiva 3d */
    transition: transform .9s;
    /* efeito de movimento do flip do card */
}

.card:active {
    transform: scale(0.97);
    transition: transform .2s;
}


/* Frente e Verso Cards */

.card-front,
.card-back {
    width: 100%;
    height: 100%;
    padding: 20px;
    position: absolute;
    border-radius: 5px;
    background: rgb(92, 187, 182);
    backface-visibility: hidden;
}


/* Trocar o verso transparente por verso virado. */

.card-front {
    transform: rotateY(180deg);
}


/* flip card animation */

.card.flip {
    transform: rotateY(180deg);
}

footer {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: left;
    color: #FFF;
    font-family: 'Roboto';
}


/* Icons */

ul.icons {
    cursor: default;
    list-style: none;
    padding-left: 0;
}

ul.icons li {
    display: inline-block;
    padding: 0 1em 0 0;
}

ul.icons li:last-child {
    padding-right: 0;
}

ul.icons li .icon {
    color: inherit;
}

ul.icons li .icon:before {
    font-size: 1.25em;
}

footer a {
    text-decoration: none;
    color: #FFF;
}


/* Header */

#header {
    display: -moz-flex;
    display: -webkit-flex;
    display: -ms-flex;
    display: flex;
    border-bottom: solid 5px #f56a6a;
    padding: 6em 0 1em 0;
    position: relative;
}

#header>* {
    -moz-flex: 1;
    -webkit-flex: 1;
    -ms-flex: 1;
    flex: 1;
    margin-bottom: 0;
}

#header .logo {
    border-bottom: 0;
    color: inherit;
    font-family: "Roboto Slab", serif;
    font-size: 1.125em;
}

#header .icons {
    text-align: right;
}

@media screen and (max-width: 1680px) {
    #header {
        padding-top: 5em;
    }
}

@media screen and (max-width: 736px) {
    #header {
        padding-top: 6.5em;
    }
    #header .logo {
        font-size: 1.25em;
        margin: 0;
    }
    #header .icons {
        height: 5em;
        line-height: 5em;
        position: absolute;
        right: -0.5em;
        top: 0;
    }
}