header.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

header {
    position: fixed;
    width: 100vw;
    top: 0;
    height: 100px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: rgba(0, 0, 0, 0.1);
    z-index: 10;
}

header:hover {
    background-color: rgba(0, 0, 0, 0.8);
    transition: all 1s;
}

header a {
    position: absolute;
    top: 35px;
    left: 20px;
    color: white;
    text-decoration: none;
    font-size: 25px;
    font-weight: bold;
    user-select: none;
    transition: all 1s;
}

.links ul {
    display: flex;
    position: absolute;
    right: 70px;
    top: 35px;
    gap: 20px;
    list-style-type: none;
}

.links a {
    position: relative;
    top: 5px;
    display: flex;
    color: white;
    font-weight: bold;
    text-decoration: none;
    font-size: 14px;
    user-select: none;
    transition: all 1s;
    margin: 7px;
}

.links a:hover,
header a:hover {
    text-decoration: underline;
}

.links ul .headerButton {
    border: 2px solid white;
    display: flex;
    justify-content: center;
    align-items: center;
    color: white;
    width: 170px;
    height: 60px;
    border-radius: 1px;
    margin-top: -11px;
}

.links ul .headerButton:hover {
    background-color: darkblue;
    text-decoration: none;
}