The gaming field is 5x7 pairs of elements. Every pair consists of two elements
out of four possible types (colors). Player is a single element, who can move on
empty fields or can take a pair, if the player's element is present in the pair.
If a pair is taken, the player's element is swapped to the other element of the
pair. The field is scrolling down on time event or after certain moves are spend
(depending on the game mode). Game over is when there is no move for the player.
