/* General Body and Page Setup */
body {
    font-family: 'Segoe UI', sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: flex-start;
    min-height: 100vh;
    margin: 0;
    padding: 20px;
    position: relative;
    z-index: 1; /* Content is on the base layer */
}

h1 {
    color: #d16ba5;
    margin: 30px 0;
    text-align: center;
    font-size: 2rem;
    text-shadow: 1px 1px 3px rgba(255,255,255,0.5);
}

.banner {
    width: 100%;
    max-width: 700px;
    border-radius: 20px;
    margin-bottom: 20px;
}

.intro-text {
    color: #a1427b;
    text-align: center;
    max-width: 600px;
    margin: 0 0 30px 0;
    font-size: 1.7rem;
    font-family: 'Great Vibes', cursive;
    font-weight: 500;
}

.month-list {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
    width: 100%;
    max-width: 600px;
}

.month-link {
    border-radius: 15px;
    padding: 25px 15px;
    text-align: center;
    text-decoration: none;
    color: #ff758f;
    font-weight: bold;
    font-size: 1rem;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    transition: transform 0.2s;
    background-color: rgba(255,255,255,0.7);
    backdrop-filter: blur(5px);
    position: relative;
    overflow: hidden;
}

.month-link:hover {
    transform: scale(1.05);
}

.month-with-bg {
    background: transparent;
    backdrop-filter: none;
    color: #c95d90;
    text-shadow: 0 0 10px white;
}

.month-with-bg::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background-image: var(--bg-image);
    background-size: cover;
    background-position: center;
    border-radius: 15px;
    z-index: -2;
}

.month-with-bg::after {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background-color: rgba(255, 255, 255, 0.4);
    backdrop-filter: blur(2px);
    border-radius: 15px;
    z-index: -1;
}

.birthday-link {
    background: linear-gradient(135deg, #fcb6c7, #f88da6);
    color: white;
    text-shadow: none;
}
.birthday-link:hover {
    background: linear-gradient(135deg, #f88da6, #fcb6c7);
}

.locked {
    background: #ddd;
    color: #888;
    cursor: not-allowed;
    text-shadow: none;
}
.locked::after {
    content: '\1F512';
    position: absolute;
    top: 10px;
    right: 10px;
    font-size: 20px;
}
.empty-cell {
    visibility: hidden;
}
@media (max-width: 600px) {
    .month-list {
        grid-template-columns: repeat(2, 1fr);
    }
    .intro-text {
        font-size: 1.5rem;
    }
}