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

header {
    background-color: #f0f0f0;
    padding: 20px;
    text-align: center;
}

.contenedor {
    padding: 20px;
    max-width: 1000px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 30px;
}

.unidad {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.rectangulo {
    background-color: #3498db;
    height: 50px;
}

.px {
    width: 300px;
}

.porcentaje {
    width: 50%;
}

.em {
    width: 20em;
}

.rem {
    width: 18rem;
}

.vw {
    width: 60vw;
}

.vh {
    width: 30vh;
}

.cm {
    width: 10cm;
}

.mm {
    width: 80mm;
}

.in {
    width: 3in;
}

.pt {
    width: 200pt;
}

.pc {
    width: 15pc;
}

.ch {
    width: 30ch;
}

.ex {
    width: 25ex;
}

.descripcion {
    border: 1px solid #ddd;
    padding: 10px;
    background-color: #f9f9f9;
}

footer {
    background-color: #f0f0f0;
    padding: 10px;
    text-align: center;
    margin-top: 20px;
}