Back in 2007, Lumosity was a scrappy startup scrounging for seed money. Today, the San Francisco-based company that creates games to make your brain work better is announcing it’s landed over $32 million in new funding.

What a difference four years make.

“When we first invested, we were concerned this was just a niche area for people with Alzheimer’s or other cognitive problems,” Tim Chang of Norwest Venture Partners tells Fast Company. “But Lumosity has proved there’s universal demand for this among all demographics.”

Indeed, today, over 14 million people in 180 countries either subscribe to Lumosity’s website or have downloaded one of its iPhone apps. And revenues have grown 25% every quarter since its launch.

Other companies, like CogniFit and Posit Science, also compete in this space, though none has received as large a round of funding as Lumosity. Sharp Brains, a market research firm tracking the brain fitness space, estimates that the size of the market for digital products was just under $300 million in 2009 and will grow to at least $2 billion by 2015.

Lumosity’s website offers 40 games designed to sharpen a wide range of cognitive skills. The signup process walks you through a series of questions to figure out whether you want, for example, to improve your ability to remember names, get better at problem solving, or develop better concentration at work or while driving. It then designs a series of “courses” tailored to your particular interests.