header {
    position: sticky;
    top: 0;
    z-index: 10;
    width: 100%;
    box-shadow: 0 2px 8px rgba(0,0,0,0.08);
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    background-color: rgba(224, 231, 255, 0.65);
}

header.scrolled {
    position: fixed;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    background-color: rgba(224, 231, 255, 0.65);
}

header .d-flex {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

header img {
    height: 95px;
}

.button-container {
    display: flex;
    align-items: center;
}

.button-container .btn {
    margin-left: 10px;
    color: white;
    background-color: #9b9b9b;
    border: none;
    padding: 8px 14px;
    border-radius: 6px;
    text-decoration: none;
    font-weight: 600;
    transition: background-color 0.3s ease;
}

.button-container .btn:hover {
    background-color: #9b9b9b;
}

.burger-btn {
    background: none;
    border: none;
    cursor: pointer;
    display: none;
    padding: 8px;
    position: relative;
    width: 36px;
    height: 28px;
    z-index: 20;
    color: #ccc;
}

.burger-line {
    display: block;
    width: 100%;
    height: 4px;
    background-color: currentColor;
    margin-bottom: 6px;
    border-radius: 2px;
    transition: transform 0.3s ease, opacity 0.3s ease;
}

.burger-btn[aria-expanded="true"] .burger-line:nth-child(1) {
    transform: translateY(10px) rotate(45deg);
}

.burger-btn[aria-expanded="true"] .burger-line:nth-child(2) {
    opacity: 0;
}

.burger-btn[aria-expanded="true"] .burger-line:nth-child(3) {
    transform: translateY(-10px) rotate(-45deg);
}

@media (max-width: 991px) {
    header .d-flex {
        justify-content: space-between;
        position: relative;
    }

    .burger-btn {
        position: absolute;
        right: 20px;
        top: 50%;
        transform: translateY(-50%);
        display: block;
        z-index: 20;
    }

    .button-container {
        position: absolute;
        top: 116%;
        left: 0;
        width: 100%;
        max-height: 0;
        overflow: hidden;
        flex-direction: column;
        background-color: #1a1a1a;
        transition: max-height 0.35s ease;
        box-shadow: 0 4px 12px rgb(155, 155, 155);
        border-bottom-left-radius: 8px;
        border-bottom-right-radius: 8px;
        z-index: 15;
        padding-top: 10px;
    }

    .button-container.open {
        max-height: 300px;
    }

    .button-container .btn {
        width: 90%;
        margin: 10px auto;
        text-align: center;
        font-size: 1.1rem;
        background-color: #9b9b9b;
    }
}

@media (max-width: 767px) {
    header img {
        height: 100px;
    }
    .button-container .btn {
        font-size: 1rem;
        margin: 8px auto;
        width: 90%;
    }
    header .d-flex {
        padding-left: 15px;
        padding-right: 15px;
    }
}

@media (max-width: 480px) {
    header img {
        height: 70px;
    }
    .button-container .btn {
        font-size: 0.9rem;
        padding: 6px 8px;
        width: 95%;
    }
}