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";

button {
  all: unset;
}

window.Agenda {
  > button {
    margin: 24px;
    > box {
      /* From https://css.glass */
      font-size: 1.8em;
      text-shadow: 0px 0px 3em #000000;
      background: rgba(0, 0, 0, 0.2);
      border-radius: 16px;
      box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
      border: 1px solid rgba(0, 0, 0, 0.3);
      padding: 24px;
    }
  }
}