body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  align-items: baseline;
  flex-flow: column;
}
.contenedor {
  max-width: 1000px;
  margin: auto;
  position: relative;
}

header {
  height: 80px;
  width: 100%;
  display: flex;
  background: lightgrey;
  justify-content: flex-end;
  text-align: center;
  line-height: 80px;
}

.logo img {
  height: 70px;
}
.logo {
  position: absolute;
  left: 0;
  width: 0;
  transition: .5s;
  margin-top: 5px;
  margin-left: 50px;
}
.banner {
  position: absolute;
  background-image: url("../img/MediaQueries.jpg");
  background-position: center;
  background-size: cover;
  height: 80px;
  width: 30%;
  left: 40%;
  transition: .5s;
  top: 0;
  z-index: 2;
}
.menu {
  position: absolute;
  background: orange;
  width: 30%;
  transition: .5s;
  top: 0;
  left: 70%;
}
.menu ul {
  display: flex;
  margin: 0;
  padding: 0;
  justify-content: space-around;
}
li {
  list-style-type: none;
}
a {
  color: blue;
  text-decoration: none;
  position: relative;
}
section {
  text-align: center;
  transition: 1s;
  display: flex;
  flex: 1;
}
.css {
  display: inline-block;
  transition: .5s;
  position: relative;
  width: 70%;
  background: skyblue;
  margin-top: 0;
}
.mq {
  display: inline-block;
  top: 0;
  position: relative;
  width: 30%;
  background: violet;
  transition: .5s;
}

footer {
  background: lightgreen;
  height: 100px;
  width: 100%;
  text-align: center;
}

@media screen and (max-width: 768px) {
  .logo {
    margin-left: 0;
    width: 60%;
    text-align: center;
  }
  .banner {
    top: 80px;
    left: 60%;
    width: 40%;
  }
  .menu {
    width: 40%;
    left: 60%;
  }
  .mq {
    top: 80px;
    width: 40%;
  }
  .css {
    width: 60%;
  }
}
@media screen and (max-width: 640px) {
  .logo {
    width: 100%;
  }
  .menu {
    top: 80px;
    left: 0;
    width: 60%;
    z-index: 2;
  }
  .css {
    margin-top: 80px;
  }
}
@media screen and (max-width: 480px) {
  .banner {
    left: 0;
    top: 160px;
    width: 100%;
  }
  .css {
    margin-top: 160px;
    width: 100%;
    height: auto;
  }
  .menu {
    width: 100%;
  }
  .mq {
    margin: 0;
    top: 0;
    width: 100%;
    height: auto;
    align-self: flex-end;
  }
  section {
    flex-direction: column;
  }
}