A start fill scheme in a first layer that is initially non-transparent is displayed on a display of a computing device. An end fill scheme in a different second layer that overlaps the first layer and is initially at least partially transparent is displayed on the display. A first transparency value of the first layer is gradually changed to a value corresponding to transparency. A second transparency of the second layer is gradually changed to a value corresponding to non-transparency. Both the first transparency value and the second transparency value are gradually changed during a particular time period. Gradually changing the first transparency value and the second transparency value includes changing the values by a plurality of increments over the particular time period.