body {
    background-color: #1a1a2a;
    color: #ffffff;
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

header.header {
    text-align: center;
    background-color: #1e1e2f;
    color: #fff;
    padding: 20px 10px;
}

.header img {
    height: 130px;
    margin-bottom: 10px;
}

h1 {
    margin: 0;
    font-size: 1.8em;
}

input#elementSearch {
    margin: 20px auto 10px auto;
    display: block;
    padding: 10px;
    font-size: 16px;
    width: 300px;
    border-radius: 6px;
    border: 1px solid #ccc;
}

button#exportButton {
    display: block;
    margin: 5px auto 20px auto;
    padding: 8px 16px;
    font-size: 14px;
    border-radius: 6px;
    background-color: #3e7cb1;
    color: #fff;
    border: none;
    cursor: pointer;
}

button#exportButton:hover {
    background-color: #346392;
}

.periodic-table {
    display: grid;
    grid-template-columns: repeat(18, 60px);
    grid-auto-rows: 60px;
    gap: 6px;
    justify-content: center;
    margin: 10px auto;
    padding: 20px;
    background-color: #3b4b72; /* Slate blue */
    border-radius: 8px;
}

.element {
    border: 1px solid #ccc;
    border-radius: 6px;
    padding: 5px;
    text-align: center;
    cursor: pointer;
    display: flex;
    flex-direction: column;
    justify-content: center;
    font-weight: bold;
    transition: transform 0.2s, opacity 0.2s ease;
    color: #000;
    opacity: 0;
    animation: fadeIn 0.8s ease forwards;
}

.element.dark-bg {
    color: #fff;
}

.element.light-bg {
    color: #000;
}

.element.hidden {
    visibility: hidden;
    opacity: 0;
    pointer-events: none;
}

.element:focus {
    outline: 2px solid #66ccff;
}

@keyframes fadeIn {
    to {
        opacity: 1;
    }
}

.modal {
    display: none;
    position: fixed;
    z-index: 10;
    left: 0; top: 0;
    width: 100%; height: 100%;
    overflow: auto;
    background-color: rgba(0,0,0,0.7);
}

.modal-content {
    background-color: #2a2a3d; /* dark modal background */
    margin: 5% auto;
    padding: 20px;
    width: 90%;
    max-width: 600px;
    border-radius: 10px;
    color: #fff;
}

.modal-content img {
    max-width: 300px;
    display: block;
    margin: 10px auto;
}

model-viewer {
    width: 100%;
    height: 300px;
    margin-top: 10px;
}

.close {
    float: right;
    font-size: 24px;
    font-weight: bold;
    cursor: pointer;
    color: #fff;
}

footer.footer {
    margin-top: auto;
    padding: 20px 10px;
    text-align: center;
    background-color: #1e1e2f;
    color: #fff;
    font-size: 0.9em;
    display: flex;
    flex-direction: column;
    align-items: center;
}

footer.footer img {
    margin-top: 10px;
    height: 60px;
}

@media (max-width: 768px) {
    .periodic-table {
        grid-template-columns: repeat(9, 50px);
        grid-auto-rows: 50px;
    }

    .element {
        font-size: 12px;
    }

    input#elementSearch,
    button#exportButton {
        width: 90%;
    }

    .modal-content {
        width: 95%;
    }
}