#+HTML_HEAD_EXTRA: <style> .my-svg-class { width: 30vw; } </style>

* styling with default class
  #+BEGIN_SRC asymptote :file svg-image.svg
    size (1cm, 0);
    fill (unitsquare, red);
  #+END_SRC

  #+RESULTS:
  [[file:svg-image.svg]]

* styling with class specified with attribute

  #+ATTR_HTML: :class my-svg-class
  [[file:svg-image.svg]]

* going back to default class
  [[file:svg-image.svg]]
* case where class id nil (no CSS class)
  #+ATTR_HTML: :class nil
  [[file:svg-image.svg]]