Referencing Parent Selectors: &

& must appear at the beginning of a compound selector, but it can be followed by a suffix that will be added to the parent selector. For example:

```
#main {
  color: black;
  &-sidebar { border: 1px solid; }
}
```

'-sidebar' should have the same color as 'main'
colorization working properly for '&: hover'

an other mistake with '-on'

```
&-on {
  background-color: $myColor;
}

```
