main.css

* {
    box-sizing: border-box;
}

body {
    background-color: rgb(32, 49, 88);
    color:black;
    font-family: Arial, Helvetica, sans-serif;
}

#chatBox {
    width:100%;
    position:absolute;
    bottom:70px;
    top:60px;
    right:0px;
    left:0px;
    background:#eee;
    border:1px solid #333;
}

#chatInput {
    position:fixed;
    left:0px;
    bottom:0;
    width:100%;
    background-color:#ccc;
    display: flex;
    justify-content: space-between;
    height: 70px;;
}

#chatInput input {
    width:100%;
}

#chatInput button {
    margin:0px 10px;
}