body {
    margin: 0;
    font-family: 'Noto Sans KR', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    overflow: hidden; /* Prevents scrollbars from main page */
}

.portal-container {
    display: flex;
    gap: 40px;
    flex-wrap: wrap;
    justify-content: center;
    padding: 20px;
    transition: opacity 0.5s ease;
}

.portal-card {
    background: rgba(255, 255, 255, 0.1);
    border-radius: 20px;
    padding: 40px;
    width: 300px;
    text-align: center;
    text-decoration: none;
    color: white;
    box-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.2);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.2);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    cursor: pointer;
}

.portal-card:hover {
    transform: translateY(-15px) scale(1.05);
    box-shadow: 0 16px 40px 0 rgba(0, 0, 0, 0.3);
}

.portal-card h2 {
    margin-top: 0;
    font-size: 1.8em;
    font-weight: 700;
}

.portal-card p {
    font-size: 1.1em;
    font-weight: 400;
    opacity: 0.9;
}

/* Styles for Iframe and Nav Bar */
.hidden {
    display: none !important;
}

#iframe-container {
    position: absolute;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: transparent; /* Removed background color */
    display: flex;
    flex-direction: column;
    transition: opacity 0.5s ease;
}

#iframe-nav {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 15px;
    background: rgba(0, 0, 0, 0.2);
    backdrop-filter: blur(5px);
    -webkit-backdrop-filter: blur(5px);
    gap: 20px;
    width: 100%;
    box-sizing: border-box;
}

.nav-button, #back-button {
    padding: 10px 20px;
    background-color: rgba(255, 255, 255, 0.1);
    color: white;
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 10px;
    font-size: 1em;
    font-family: 'Noto Sans KR', sans-serif;
    cursor: pointer;
    transition: background-color 0.3s ease, transform 0.2s ease;
}

.nav-button:hover, #back-button:hover {
    background-color: rgba(255, 255, 255, 0.3);
    transform: translateY(-2px);
}

.nav-button.active {
    background-color: rgba(255, 255, 255, 0.4);
    box-shadow: 0 0 15px rgba(255, 255, 255, 0.3);
}

#back-button {
    background-color: rgba(0, 0, 0, 0.4);
}

#content-frame {
    flex-grow: 1; /* Take remaining space */
    border: none;
}