blog/themes/embark/source/css/01-tools/_tools.placeholder.scss

// Placeholder
@mixin placeholder {
  &::-webkit-input-placeholder {
    @content
  }
  &:-moz-placeholder           {
    @content
  }
  &::-moz-placeholder          {
    @content
  }
  &:-ms-input-placeholder      {
    @content
  }
}