body {
    font-family: Arial, sans-serif;
    background-color: #fff;
    margin: 0;
    padding: 0;
}
.header {
    position: sticky;
    top: 0;
    background-color: #fff;
    text-align: center;
    padding: 10px;
    z-index: 1000;
    border-bottom: 1px solid #ccc;
}
.logo {
    width: 150px;
    display: block;
    margin: 0 auto 10px;
}
.harver-logo {
    width: 80px;
    vertical-align: middle;
    margin-left: 10px;
}
.source {
    font-size: 14px;
    margin-bottom: 5px;
}
.button-group {
    margin: 0;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
}
.btn {
    padding: 10px 20px;
    margin: 10px;
    font-size: 16px;
    cursor: pointer;
    border: none;
    border-radius: 5px;
    font-weight: bold;
}
.level1 {
    background-color: #00bcd4;
    color: #000;
}
.level2 {
    background-color: #001f5b;
    color: #fff;
}
.pdf-container {
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #fff;
    width: 100%;
    height: 90vh;
    margin-top: 0;
}
.pdf-container embed {
    width: 100%;
    height: 100%;
    border: none;
    background-color: #fff;
}
.hidden {
    display: none;
}

/* Responsive Design */
@media (max-width: 768px) {
    .logo {
        width: 120px;
    }
    .harver-logo {
        width: 60px;
    }
    .btn {
        width: 90%;
        font-size: 14px;
    }
    .pdf-container {
        height: 70vh;
    }
    .pdf-container embed {
        width: 100%;
        height: 100%;
    }
}

@media (max-width: 480px) {
    .btn {
        width: 100%;
        margin: 5px 0;
    }
    .header h1 {
        font-size: 18px;
    }
    .header p {
        font-size: 14px;
    }
}