DreamBox launched its game this week after more than two years of development and testing, including trial runs at several schools in the Seattle area. It joins a crowded field of educational games and software with a $13-a-month subscription service that may be a hard sell in lean times.

But its founders, former top Microsoft executive Ben Slivka and startup veteran Lou Gray, believe they'll succeed with fun yet sophisticated software.

Drawing from advances in e-commerce, the company built a system that monitors students' activity and progress, then uses that information to dynamically customize the programs for each user.

Marshall said that capability won her over, more than the gaming.

"I'm incredibly impressed by the fact I can have my entire class of second graders sitting there and they will be in 15 or 20 different places in the program beause it is so perfectly matched to their level of need,'' she said.

In the program, aimed at 5- to 8-year-olds, children create custom avatars and choose from four adventure game themes -- pirate, pixie, dinosaur and pets -- each with eight stories. Altogether, the system has more than 350 math lessons, developed and vetted by teachers.

DreamBox is positioning itself to be a player in educational software as schools move toward more computer-based learning tools in the coming years.

"We believe we are timed right to serve a growing market, not only in the home but over time in the school,'' said Gray, the chief executive, who earlier led the sale of Bellevue mobile software firm UIEvolution to Square Enix for $58 million.

DreamBox's 21 employees also include developers from Microsoft, Amazon.com, Expedia and VMWare.

The "GuideRight" customization system they built is one of six technologies for which DreamBox is seeking patents. Others include tools and a parent dashboard.

Eventually DreamBox may develop its technology into a platform and open it up to other educational content developers. It's even created a programming language that its four staff teachers use to produce content.

(DreamBox runs its own Unix servers and built its service using tools such as Flash, MySQL and Ruby on Rails.)

First they need to get the math program off the ground. Then they'll likely extend the math program to additional grades, and perhaps add science and literacy programs someday.

The program is initially intended primarily for children to use at home, although the company is interested in building its presence in schools as well. Early users have been testing the software in after-school programs, for instance.

Marshall, whose school is evaluating new math materials, said DreamBox wouldn't be the primary math curriculum, but it could be used as a supplement.

Wednesday, the day after DreamBox became publicly available, Gray wouldn't provide details about how many subscribers DreamBox has or its targets, but said, "we're beating our initial expectations."

The company has $7.1 million in funding from angel investors, including Slivka and Gray, who have offered $2 million more if needed. They're also discussing investment from venture capitalists or strategic partners.