_From @mercmobily on July 1, 2016 2:19_

If you have a simple file `test.html`:

```

window.Polymer = { lazyRegister: true, dom: 'shadow'};

h1 {
color: blue;
}

Extra CSS styles

What colour am I?

```

And `extra-styles.html` is:

```

h1 {
color: red;
}



Polymer({
is: 'extra-styles'
});

```

You will see that:

1) Using shadow DOM, the writing is blue
2) Using shady DOM, the writing is red.

This is because the style set in extra-styles is more specific:

```
h1:not([style-scope]):not(.style-scope)
```

_Copied from original issue: Polymer/polymer#3758_