index.css

body {
    margin: 0;
    padding: 0;
    text-align: center;
}

.header {
    font-family: cursive;
    margin: 0;
    padding: 6px;
}

.messages {
    display: inline-block;
    padding-bottom: 30px; /* 24 + 6 px */
    text-align: left;
}

.message {
    margin: 6px;
}

.message .avatar {
    float: left;
    width: 36px;
    height: 36px;
    background-size: 100%;
    background-repeat: no-repeat;
    border-radius: 18px;
    margin-top: 4px;
}

.message .body {
    overflow: hidden;
    position: relative;
    margin-left: 42px;
}

.message .text {
    display: inline-block;
    padding: 6px;
    background-color: #b5f0ff;
    border-radius: 24px;
}

.message .text:before, .message .text:after {
    content: " ";
}

.message .headline {
    font-size: 9pt;
}

.message .name {
    font-weight: bold;
}

.input {
    display: block;
    position: fixed;
    bottom: 6px;
    left: 6px;
    right: 6px;
    width: calc(100% - 12px);
    box-sizing: border-box;
    background: #eee;
    padding: 3px 6px;
    border: 1px solid #ccc;
    border-radius: 12px;
    height: 24px;
    line-height: 24px;
    font: inherit;
    outline: none;
}