body {
    height: 100%;
    margin: 5%;
    background-repeat: no-repeat;
    background-image: url("Dice_attack.gif");
    background-position: center center;
    background-attachment: fixed;
    background-size: cover;
    position: relative;
}
.box {
    background-color: red;
    border-style: outset;
}

.player {
    background-color: lightblue;
    border-style: outset;
    margin: auto;
    width 300px;
}
.btn {
   	background-color: blue;
    border-style: outset;
    color: white;
    padding: 15px 32px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 16px;
    margin: 4px 2px;
	-webkit-transition-duration: 0.4s; /* Safari */
    transition-duration: 0.4s;
    cursor: pointer; 
}
.btn:hover {
    background-color: purple;
}