*, *::before, *::after {
    box-sizing: border-box;
}

img {
    display: block;
    max-width: 100%;
}

body {
    margin: 0;
    background: #f5f5f5;
    font-size: 15px;
}

header {
    position: sticky;
    top: 0;
}
header h1 {
    margin: 0;
    text-align: center;
    color: #fff;
    line-height: 44px;
    font-size: 19px;
    font-weight: 400;
    background: -webkit-linear-gradient(left, #3593ff, #49c9ff);
}
.header-second {
    display: flex;
    align-items: center;
    padding: 0.75em 1em;
    background: #fff;
    color: #555;
    border-bottom: 1px solid #ccc;
}
.header-second img {
    position: relative;
    top: -2px;
    width: 18px;
    margin-right: 0.3333em;
}