gtk/demos/gtk-demo/css_shadows.css

/* You can edit the text in this window to change the
 * appearance of this Window.
 * Be careful, if you screw it up, nothing might be visible
 * anymore. :)
 */

/* This CSS resets all properties to their defaults values
 *    and overrides all user settings and the theme in use */
@import url("reset.css");
@import url("cssview.css");

/* Get a nice background for the window */
.background {
  background-color: #4870bc;
  background-image: linear-gradient(to left, transparent, rgba(255,255,255,.07) 50%, transparent 50%),
                    linear-gradient(to left, transparent, rgba(255,255,255,.13) 50%, transparent 50%),
                    linear-gradient(to left, transparent, transparent 50%, rgba(255,255,255,.17) 50%),
                    linear-gradient(to left, transparent, transparent 50%, rgba(255,255,255,.19) 50%);
  background-size: 29px, 59px, 73px, 109px;
}

.button {
  color: black;
  padding: 10px;
  border-radius: 5px;
  transition: all 250ms ease-in;
  border: 1px transparent solid;
}

.button:hover {
  text-shadow: 3px 3px 5px alpha(black, 0.75);
  icon-shadow: 3px 3px 5px alpha(black, 0.75);
  box-shadow: 3px 3px 5px alpha(black, 0.5) inset;
  border: solid 1px alpha(black, 0.75);
}

.button:active {
  padding: 11px 9px 9px 11px;
  text-shadow: 1px 1px 2.5px alpha(black, 0.6);
  icon-shadow: 1px 1px 2.5px alpha(black, 0.6);
}