button {
    display: block;
    padding: 10px 10px;
    background: #555555;
    color: #ffffff;
    border-radius: 10px;
    margin: 3px 0px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.5);
}

.subject-container {
    display: flex;
    justify-content: center;
}