Game play involves selecting 'runs' of sequential numbers from a numeric grid. Rows and columns can be moved upwards or sideways to help move a number into position, allowing longer runs of numbers, which score more points. However, to keep you on your toes, the grid automatically 'shifts' every 10 seconds or so. On each 'shift' the 'runs' that you have highlighted are scored and removed from the grid. These 'quick shifts', which give the game its name, keep the pace of game play high and reward quick thinking.

To complete a level you must score a set number of points within a given time. There are 30 levels to work through and, as you move through the levels, the game becomes more difficult. Additional numbers are added and some tiles can be locked out during game play, thus making it hard to get the score needed to complete the level.

It takes a few turns to work out the game play (aided by the in-game help screens), but once you've mastered the basics it is a surprisingly addictive game. To keep you coming back for more there's also a set of achievements to unlock (scoring certain points in one shift, using shuffles, completing the game and so on) and the usual high score table. 

The new games modes don't alter the game play, but they are harder, especially the mixed mode version. That's probably because our brains are better at spotting sequences of numbers than letters or a combination of both.