body {
    display: flex;
    min-height: 100vh;
    align-items: center;
    justify-content: center;
}
article {
    display: table;
    background-color: #eee;
    border: 1px solid #ddd;
    border-radius: 0.5rem;
    padding: 1rem;
    margin-top: 1rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1),
          0 4px 8px rgba(0, 0, 0, 0.1),
          0 8px 16px rgba(0, 0, 0, 0.1),
          0 16px 32px rgba(0, 0, 0, 0.1);
}
section {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
}
h1 {
    text-align: center;
}
.btn {
    display: flex;
    align-items: center;
    justify-content: center;
}
.btn-primary {
    background-color: #2196f3;
    color: white;
    font-weight: bold;
    border: none;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
    transition: background-color 0.3s ease-in-out;
}
.btn-primary:hover {
    background-color: #1976d2;
}
.btn-primary:active {
    box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.2);
}