* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
.container {
    width: 850px;
    height: 480px;
    margin: 0 auto;
    background: url('../images/bg.jpg');
    background-repeat: repeat-x;
    background-size: contain;
    overflow: hidden; 
    position: relative;
}
img {
    position: absolute;
    width: 100px;
    bottom: 80px;
    left: 360px;
}
.marioRunning {
    display: none;
    width: 85px;
}
#marioCrouch {
    height: 50px;
}
#marioJump {
    bottom: 280px;
}
.musicButton {
    margin-top: 2px;
    width: 250px;
    display: flex;
}
.author-container {
    width: 850px;
    height: 50px;
    margin: 0 auto;
    display: flex;
}
.title-exercise {
    margin: 0 auto;
    text-align: center;
}
.author-name {
    font-size: 0.9rem;
    text-align: right;
}