header {
    position: fixed;
    top: 0;
    left: 0;
    z-index: 1000;
    width: 100%;
    box-sizing: border-box;

    display: flex;
    justify-content: space-between;
    align-content: center;
    align-items: center;

    height: 100px;
    padding: 1vh 0;

    background-color: #FFFFFF00;
    transition: background-color 0.5s, height 0.3s ease;
}
header * {
    color: #FFF;
}
header img {
        width: 60px;
        height: 50px;
        padding-left: 30px;
        padding-right: 10px;
        cursor: pointer;
        border-top-right-radius: 10px;
        border-bottom-right-radius: 10px;
        filter: invert(1);
    }

#headerText {
    position: relative;
    font-size: 1.5rem;
    font-weight: 300;
    height: 50px;
    padding: 0px 10px 0px 5px;
    border-top-left-radius: 10px;
    border-bottom-left-radius: 10px;
    transition: background-color 0.5s;
}
#headerText strong {
    font-weight: 500;
    margin-right: 0.2em;
}

#companyName {
    transform: translateY(-5px);
    transition: transform 0.3s ease;
}

#tel {
    position: absolute;
    top: 0;
    left: 7px;
    transform: translateY(30px);

    font-size: 1rem;
    font-weight: 400;
    letter-spacing: 0.25rem;
    
    opacity: 1;
    visibility: visible;
    transition: opacity 0.3s ease, visibility 1s ease;
}

header img {
    transition: opacity 0.3s ease-in-out;
}

.image-transition {
    opacity: 0;
}

.image-transition.loaded {
    opacity: 1;
}

@media (max-width: 768px) {
    header {
        padding: 1vh 0;
        height: 70px;
    }
    header img {
        width: 50px;
        height: 40px;
    }
    #headerText {
        font-size: 1rem;
        height: 40px;
    }
    #tel {
        font-size: 0.7rem;
    }
    
}