Usually, I would move mixins to the top and separate them from the other style information by a newline. You inserted them alphabetically, ignoring the dot, which is another good and valid approach. What would you prefer?
```
.ip-menu-bar {
  background: #363636;
  .box-shadow(4px 0 2px 0 #222);
  color: #fff;
}
```

vs.

```
.ip-menu-bar {
  .box-shadow(4px 0 2px 0 #222);

  background: #363636;
  color: #fff;
}
```