this should extend the `btn` class we already have. and call it `btn-play` if the style needs to be more specific (I don't think it needs to). you should probably just replace `.btn` so it has the following (copied from Sketch):

```css
background: #40DFC2;
border-radius: 4px;
border: 1px solid rgba(63,223,193,.8);
box-shadow: inset 0px -1px 0px 0px rgba(0,0,0,.1);
```