:root {
    --card-w: 180px;
    --p-h: 130px;
    --btn-h: 35px;
    --border-size: 1px;
}

body {
    margin: 0;
    padding: 0;
    font-family: "Proxima Nova", sans-serif;
    font-size: 14px;
}

* {
    outline: none;
    box-sizing: border-box;
}


h2 {
    font-size: 20px;
    margin: 15px 0;
}

a {
    color: black;
}

.page {
    max-width: 650px;
}

.cards {
    font-size: 0;
}

.card {
    width: var(--card-w);
    display: inline-block;
    font-size: 12px;
    height: calc( var(--p-h) + var(--btn-h) + var(--border-size) * 2 );
    overflow: hidden;
    margin-right: 20px;

}

.card:last-child {
    margin-right: 0;
}

.card img {
    display: block;
    max-width: 100%;
}

.buttons {
    margin: 0;
    white-space: nowrap;
    font-size: 0;
    text-align: right;
}

.buttons input {
    border-top: var(--border-size) solid #CCCCCC;
    border-right: var(--border-size) solid #CCCCCC;
    border-bottom: none;
    border-left: none;
 
    height: var(--btn-h);
    background: #F0F0F0;
    color: #6F6F6F;
    display: inline-block;
    cursor: pointer;
    font-size: 13px;
    font-weight: 700;
    text-transform: uppercase;
}

.buttons input:first-child {
    float: left;
    border-bottom-left-radius: 2px;
	width: 50%;
}
.buttons input:last-child {
    border-bottom-right-radius: 2px;
    border-right: none;
	width: 50%;
}

.buttons input:hover {
    background: rgba(240, 240, 240, 0.8);
}

.row {
    height: calc( var(--p-h) + var(--btn-h) + var(--border-size) * 2 + 30px );
}

.front, .back p {
    border: var(--border-size) solid #CCCCCC;
    border-radius: 1px;
}

.front {
    font-size: 0;
}
.front, .back {
    background: white;
}

.again {
    font-size: 18px;
    font-weight: bold;
    text-align: center;
    visibility: hidden;
    position: relative;
    top: -20px;
}

.text {
    display: none;
}

.container {
    display: inline-block;
    position: relative;
    width: 100%;
}
.container:before {
    content: "";
    display: block;
    margin-top: var(--p-h);
}

p {
    margin: 0;
    padding: 22px;

    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    border: none;

    display: inline-flex;
    justify-content: center;
    align-items: center;
    text-align: center;

    font-size: 13px;
}

.container, .front, .back, .inner, .text, .buttons {
    backface-visibility: hidden;
}

.correct {
    background-color: rgba(144, 238, 144, 0.5);
}
.correct p {
    border-color: rgba(176, 214, 176, 1);
}
.incorrect {
    background-color: rgba(240, 128, 128,0.2);
}
.incorrect p {
    border-color: rgba(214, 176, 183, 1);
}