style.css

body {
	font-family:"lato";
    
    padding-bottom:700px;
    background: 
    linear-gradient(
    rgba(135, 206, 250, 0.7), /* Bleu clair */
    rgba(70, 130, 180, 0.8), /* Bleu acier */
    rgba(25, 25, 112, 0.9)   /* Bleu nuit */
    );
    background-size: cover;
    
    }

/* Login */

#square {
    position: relative;
        width: 800px;
        height: 450px;
    display: block;
    margin: auto;
        background: #F3F6F8;
    z-index: 3;
	font-family: sans-serif;
}
        
#leftSquare {
    width: 40%;
    display: block;
    margin:  auto;
    height: 100%;
    position: absolute;
    top: 0%;
    left: 0%;
        background:linear-gradient(
        rgba(135, 206, 250, 0.7), /* Bleu clair */
        rgba(70, 130, 180, 0.8), /* Bleu acier */
        rgba(25, 25, 112, 0.9)   /* Bleu nuit */
        ),  url("https://images.pexels.com/photos/1852/dawn-landscape-mountains-nature.jpg?h=350&auto=compress");
    background-size: cover;
    border-radius: 0%;
    z-index: 1;
}
    
#rightSquare {
        width: 60%;
    display: block;
    margin:  auto;
        height: 100%;
    position: absolute;
    top: 0%;
    right: 0%;
        background:none;
    background-size: cover;
    border-radius: 0%;
    z-index: 1;
    }
    
#circle{
        border-radius: 50%;
        width: 60%;
        height: 40%;
        display: block;
        margin: auto;
        position: absolute;
        top: 8%;
        right: 20%;
    }