The bulk of Brain Age Express is devoted to the basic math minigames found in the previous Brain Age releases. You'll find such hits as "Calculations X 20" and "Calculations X 100" in the training section. There are eight training games in all, giving you plenty of opportunities to add numbers together, subtract them from one another, and other, somewhat more complicated tasks. You can also do a "brain age check," which uses your score on three random tests to generate a number used to measure, well, how quickly and accurately you can accomplish these math-based tasks. Not that it was ever full-on science, but when you reduce the core Brain Age concept to only include your math prowess, it becomes an even more abstract concept.
In addition to the math stuff, there is also a themes section that uses the DSi's built-in camera. It'll ask you to make faces that match specific moods or activities, like singing a karaoke song, looking like you've done something evil, and so on. The themes section also has you draw various things, like a panda, or Beethoven. There's also an audio theme where you record lines from a brief western script. The main idea is to have a bunch of friends also do the themes, giving you a look at how different people approach the different tasks. If you're playing alone, it's sort of a waste.
But in the end, it's the price that serves as Brain Age Express: Math's biggest enemy. At 800 points, this slice of Brain Age is nearly half of the retail price of Brain Age or Brain Age 2, both of which would be a more valuable purchase than this downloadable edition.