Here is the game to test your presence of mind. All you need to do is to get the gems of same variety in a line to destroy them and your time scale is proportionate to number of lines you make so be quick enough to identify the gems and get them in a straight lines. When you destroy the gems, the placement of the existing gems are shifted, for the new gems falls in to the screen, so use your mind to calculate the gems and form the line to destroy it.