html, body {
    height: 100%;
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    overflow: hidden;
}

body {
    font-family: Arial, sans-serif;
    background: aliceblue;
    height: 100vh;
    overflow-y: auto;
}

header, footer {
    position: fixed;
    left: 0;
    width: 100%;
    height: 10vh;
    background: steelblue;
    color: white;
    text-align: center;
    z-index: 10;
    display: flex;
    align-items: center;
    justify-content: center;
}

header {
    top: 0;
}

footer {
    bottom: 0;
}

.principal {
    background: honeydew;
    padding: 30px 0;
    position: absolute;
    top: 10vh;
    bottom: 10vh;
    left: 0;
    right: 0;
    overflow-y: auto;
    overflow-x: hidden;
    height: 80vh;
}

form {
    width: 80%;
    margin: 0 auto;
}

.fila-formulario {
    display: flex;
    justify-content: space-between;
    margin-bottom: 30px;
    gap: 2%;
}

.grupo-formulario {
    flex: 0 0 48%;
    display: flex;
    flex-direction: column;
}

label {
    font-weight: bold;
    margin-bottom: 8px;
    color: darkslategray;
}

input[type="text"],
input[type="number"],
select {
    padding: 10px;
    font-size: 1.1em;
    border: 1px solid teal;
    border-radius: 2px;
    background: white;
}

button[type="submit"] {
    width: 100%;
    padding: 18px 0;
    font-size: 1.2em;
    background: orange;
    border: 1px solid darkorange;
    border-radius: 2px;
    cursor: pointer;
    font-weight: bold;
    color: white;
}

button[type="submit"]:hover {
    background: darkorange;
}

footer h3 {
    margin: 0;
    padding: 10px 0;
}

@media (max-width: 700px) {
    .fila-formulario {
        flex-direction: column;
        gap: 0;
    }
    .grupo-formulario {
        width: 100%;
        margin-bottom: 15px;
    }
    form {
        width: 95%;
    }
}