h1 {
    background-color: burlywood;
    color: darkgreen;
    font-size: 100%;
}

div.headline {
    display: flex;
    justify-content: space-evenly;
    align-items: center;
}

img.headline {
    width: 20%;
    height: 20%;
    margin: 10px;
}

p.headline {
    text-align: center;
}

table.grammar {
    text-align: center;    
    border: solid 1px green;
}

table.grammar td, table.grammar th {
    border: solid 1px green;
    padding: 2px;
    white-space: nowrap;
}

table.grammar td:nth-child(1), table.grammar th {
    font-weight: bold;
}

strong {
    color: lightseagreen;
}

p {
    margin: 0;
}

#cards {
    display: flex;
    justify-content: center;
    margin-bottom: 10px;
}

.card {
    width: 109px;
    height: 165px;
    perspective: 1000px;
    cursor: pointer;
}

.card img {
    width: 100%;
    height: 100%;
}

.card-inner {
    width: 100%;
    height: 100%;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 1s;
}

.card-front, .card-back {
    width: 100%;
    height: 100%;
    position: absolute;
    backface-visibility: hidden;
    border: solid black 1px;
    border-radius: 8px;
}

.card-front {
    transform: rotateY(0deg);
}
  
.card-back {
    font-size: 50px;
    color: darkgreen;
    background-color: burlywood;
    transform: rotateY(180deg);
    display: flex;
    justify-content: center;
    align-items: center;
}

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