asciinema.org/app/views/asciicasts/_player.html.slim

.player class="#{options.size}-font"

javascript:
  $(function() {
    var playerClass = #{options.player_class};
    var maxWidth = #{options.max_width || 'null'};

    window.player = new playerClass({
      el:            $('.player'),
      speed:         #{options.speed},
      benchmark:     #{options.benchmark},
      model:         new Asciinema.Asciicast(#{asciicast.html_safe}),
      maxWidth:      maxWidth || $('.cinema .player').parent().width(),
      rendererClass: #{options.renderer_class},
      autoPlay:      #{options.autoplay},
      hud:           #{!options.hide_hud}
    });
  });