body {
    position: relative;
    text-align: center;
    background-color: green;
}

#gameCanvas {
    background: url(images/background_grass.jpg) center;
    background-size: 800px;
    border: 1px solid darkgreen;
    /* Start the shake animation and make the animation last for 0.5 seconds */

    /* When the animation is finished, start again */
    animation-iteration-count: infinite;
}

#gameOverContainer,
#rulesContainer {
    box-sizing: border-box;
    position: absolute;
    top: 0;
    width: 100%;
    padding: 8px;
}

#gameOver,
#rules {
    width: 60%;
    margin: auto;
    background-color: lightblue;
    color: black;
    text-align: left;
    border: 1px solid blue;
    margin-top: 30px;
    padding: 8px;
    height: 500px;
    display: flex;
    justify-content: center;
    align-items: center;
}

.hidden {
    display: none !important;
}

.shake {
    animation: shake 0.5s;
}

@keyframes shake {
    0% {
        transform: translate(1px, 1px) rotate(0deg);
    }

    10% {
        transform: translate(-1px, -2px) rotate(-1deg);
    }

    20% {
        transform: translate(-3px, 0px) rotate(1deg);
    }

    30% {
        transform: translate(3px, 2px) rotate(0deg);
    }

    40% {
        transform: translate(1px, -1px) rotate(1deg);
    }

    50% {
        transform: translate(-1px, 2px) rotate(-1deg);
    }

    60% {
        transform: translate(-3px, 1px) rotate(0deg);
    }

    70% {
        transform: translate(3px, 1px) rotate(-1deg);
    }

    80% {
        transform: translate(-1px, -1px) rotate(1deg);
    }

    90% {
        transform: translate(1px, 2px) rotate(0deg);
    }

    100% {
        transform: translate(1px, -2px) rotate(-1deg);
    }
}