Grockit games can now be customized by skill tags and difficulty level.  This helps you optimize your study time.  Custom games are best explained with an example.

They work something like this;  Sue is studying for the GMAT and her Grockit analytics indicate she needs the most improvement on Verbal questions.  More specifically, Sentence Correction and Idioms give her the most trouble.  Knowing this, Sue creates a custom game and selects the Sentence Correction and the Idiom skill tags to include.  This creates a game which only contains these two types of questions. You can see the summary that Sue sees when she is creating the game in this picture.

In addition, Sue can adjust the difficulty level of the questions to her level of ability.  In short, custom games make it easier than ever for Sue to optimize her study time and concentrate on the areas she needs the most practice.