This free app is intended to help improve your working memory by allowing you to memorise an increasingly large grid of coloured jewels.
"Working memory is a central intellectual faculty, linked to IQ, ageing, and mental health. It has been claimed that working memory training programs are effective means, not only for treating attention-deficit/hyperactivity disorder (ADHD) and other childhood disorders, but to improve intelligence and school attainment in all children and adults." -- Wikipedia