Tiles are aligned by swapping ones adjacent to each other. If this causes a line of three or more matching tiles to form, the tiles stay in their new position and the matching tiles are removed. If no line of three or more matching tiles is formed the tiles revert to their original position. Lines can be horizontal or vertical, and combinations can cause many lines to disappear at the same time. When tiles disappear, any tiles above them on the screen fall down to fill the space. If this results in a further line of three, this line also disappears. This is called a 'chain'. An example of a chain can be seen in the screenshot: making a line of (green) crocodiles in the centre of the screen will cause the crocodiles to disappear, and the (red) gorillas will meet to make a line of three.