GREG is a mathematical puzzle game for iPhone that will enhance your mental flexibility. The goal of GREG is to sum the numbers written on the tokens in the grid to reach a given number as quickly as possible. Every time the game timer reach the end all the tokens become hotter until they become black and burn. The game ends when a single token burns. To cool down the tokens you must use them for a correct sum. GREG features an unique algorithm that increases the game difficulty as the user reaches higher levels. GREG has been developed on a solid concept of gamification. Every time you play you earn gold which is used to purchase special items to help the user in the game. It also features different types of leaderboards, exciting achievements and an innovative multiplayer mode via Bluetooth LE. Source: The Developer Website.