body {
  background-color: #66a2c9;
  background-image: repeating-linear-gradient(
    45deg,
    #5f99c0 0,
    #5f99c0 10px,
    #66a2c9 10px,
    #66a2c9 20px
  );
  font-family: Arial, sans-serif;
}

.contenedor {
  width: 80%;
  margin: 50px auto;
  background-color: #808080;
  border: 3px solid #333;
  box-shadow: 0 0 10px #0004;
}

.titulo {
  background-color: #bfbfbf;
  text-align: center;
  font-size: 24px;
  padding: 10px;
  border-bottom: 4px double #222;
}

.bloques {
  display: flex;
  justify-content: space-between;
  padding: 20px;
}

.bloque {
  flex: 1;
  margin: 0 10px;
  padding: 20px;
  font-weight: bold;
  text-align: center;
}

.uno { background-color: #ffffcc; }
.dos { background-color: #ccccff; }
.tres { background-color: #ffcccc; }