$asset-list: () !default;
$asset-list: map-merge(
  (
    "action-font-size": 0.75rem,
    "thumbnail-gutter": 15px,
    "thumbnail-ratio": calc(4 / 3),
    "thumbnail-center": false
  ),
  $asset-list
);

@function asset-list($key) {
  @return map-get($asset-list, $key);
}