body {
    font-family: Arial;
    margin: 0;
    padding: 0;
}

header, footer {
    background: #333;
    color: white;
    text-align: center;
    padding: 10px;
}

nav {
    background: #ddd;
    padding: 10px;
    text-align: center;
}

button {
    padding: 8px;
    margin: 5px;
    cursor: pointer;
}

.grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
    padding: 10px;
}

.oculto {
    display: none;
}

.error {
    color: red;
}

.correcto {
    color: green;
}

.oscuro {
    background: black;
    color: white;
}

/* RESPONSIVE */
@media (max-width: 600px) {
    .grid {
        grid-template-columns: 1fr;
    }
}