style.css

@import url('https://fonts.googleapis.com/css2?family=Press+Start+2P&display=swap');

html,
body {
    width: 100%;
    height: 100%;
    margin: 0;
}

body {
    background-image: url(./img/board-bg.jpg);
    background-position: center;
    background-size: cover;
    background-repeat: no-repeat;
    overflow: hidden;
}

.author {
    font-family: 'Press Start 2P', cursive;
    text-shadow: -3px -1px 0 #b02157, 3px 1px 0 #e7a538;
    color: white;
    position: absolute;
    top: 0.5em;
    left: 0.5em;
}

a {
    color: currentColor;
    text-decoration: none;
}

.points,
.message {
    font-family: 'Press Start 2P', cursive;
    font-size: 60px;
    text-shadow: -3px -1px 0 #b02157, 3px 1px 0 #e7a538;
    color: white;
}

.points {
    text-align: right;
    position: absolute;
    top: 0.5em;
    right: 0.5em;
}

.crosshair {
    display: none;
    border: 5px solid #fffa;
    position: absolute;
    border-radius: 50%;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    pointer-events: none;
    z-index: 9;
}

.crosshair>div {
    margin: 20px;
    border-radius: 50%;
    display: inline-block;
    width: 10px;
    height: 10px;
    background-color: red;
    vertical-align: middle;
}

.board {
    width: 100%;
    height: 100%;
}

.board>.message {
    position: absolute;
    bottom: 1em;
    width: 100%;
    text-align: center;
    cursor: default;
}

#start {
    cursor: pointer;
}

a:hover,
#start:hover {
    text-decoration: underline;
}

.zombie {
    width: 200px;
    height: 312px;
    background-image: url(./img/walkingdead.png);
    background-position-x: 100%;
    background-position-y: center;
    background-size: cover;
    position: absolute;
    transition: .5s opacity;
}