AGS/style.scss

// https://gitlab.gnome.org/GNOME/gtk/-/blob/gtk-3-24/gtk/theme/Adwaita/_colors-public.scss
$theme_fg_color: "@theme_fg_color";
$theme_bg_color: "@theme_bg_color";

window.Agenda {
  > button {
    background: transparent;
    color: transparent;
    margin: 24px;
    padding: 0;
    border: 0px solid transparent;
    border-radius: 0px;
    > box {
      /* From https://css.glass */
      font-size: 1.3em;
      background: rgba(64, 47, 47, 0.32);
      border-radius: 16px;
      box-shadow: 0 4px 30px rgba(0, 0, 0, 0.1);
      border: 1px solid rgba(64, 47, 47, 0.6);
      padding: 24px;
    }
  }
}