Compared with the top-selling toys during last year’s holiday season — tablet computers for kids and “Frozen” dolls — Jeff Freeland Nelson’s Yoxo construction toys look positively old school.

Yoxo kits with chipboard cutouts of “X,” “Y,” and “O” have a retro-chic appeal for kids who haven’t yet developed a sense of anything chic or retro. With scores of pieces to work with, kids construct robots, dragonflies, dune buggies, helicopters or whatever their imagination concocts. “The future is retro,” said Freeland Nelson, who lives and has a factory in St. Paul. “The most consistent trend is the growth of building sets, dominated by Lego.” When parents or grandparents see Yoxo, they’re reminded of Tinker Toys and Erector Sets, all of which encourage kids to build and make.

Sales of Yoxo, pronounced Yock-so, and other construction sets have grown consistently 10 to 20 percent or more in the past few years, a much higher rate than toys in general, according to the NPD Group.

Freeland Nelson is seeing signs that that sales pace will continue this holiday season as large retailers have already placed orders and small retailers are doing so now. Target is expanding the line from 400 to 1,200 stores by the fall and Barnes & Noble is expanding Yoxo to 96 stores from 24.

Creative Kidstuff was the first local toy store to carry Yoxo in 2013. “We helped Jeff work on the color and size of the packaging and the price point,” said Roberta Bonoff, CEO of Creative Kidstuff. “He has a fabulous idea and he’s passionate about the product, but it wasn’t eye-catching at first.”

The sets are now packaged in thin boxes of bright green, yellow and orange at price points around $20 for most items. Amy Saldanha, owner of Kiddywampus in Hopkins, said the product sells better when kids or parents see it demonstrated compared with taking it off the shelf. “Kids love working with it. They get it before their parents do,” she said. “Once parents see the dragonfly we have on display, they see it as the open-ended educational toy they’ve been looking for.”

While Yoxo spars with Legos, Magna-Tiles and Tegu, it stands out from the competition as an eco-friendly toy made in the U.S. In 2010, 96 percent of toys were made outside of the country, according to the U.S. Department of ­Commerce.

Meanwhile, the company is launching five new products this month, including a dragon named Fyre, a Pegasus named Wynd and a female robot, Tera, which is packaged in a pink box.

Construction toys tend to be more popular with boys than girls, but Freeland Nelson, 42, consciously tries to make his product gender-neutral, with boys and girls featured on the packaging.

Manufactured in a workshop powered by wind energy through an offset program, the cutouts have been called an eco-friendly Lego alternative. But with only eight shapes in seven colors in the Yoxo collection, the comparison may not be apt. “We don’t want lots of custom pieces,” he said. “We want kids to be resourceful enough to know that they can build a dragon or a drag racer with the same parts.”

Yoxo aspires to be the most ecologically sustainable toy company in the world. The links are cut with a high-pressure water propulsion machine by Jet Edge of St. Michael, Minn. The rigid sheets from which the links are cut are 95 percent Sustainable Forestry Initiative-certified recycled wood fiber with water-based coatings. It’s one of the few toys that is not only made from recycled materials but also can be thrown in the recycling bin, unlike most plastic toys.

Eco-friendliness is important to Christine Salomon, a St. Paul resident whose 7- and 10-year-old children play with Yoxo. “I wouldn’t purchase a toy just because it’s recyclable or locally made, but it’s a huge advantage,” she said. “When my kids go to birthday parties and they bring home plastic tchotchkes, they go into the landfill when they break. Yoxo can be passed on or recycled,” she said.

Since inception, Freeland Nelson has sold about 30,000 Yoxo sets, but his product will be in about 1,400 more stores, mostly Targets, this holiday season than last year’s. With 70 sales reps and the expanded availability, he’s hoping Yoxo will boom upward from its current base of 22 employees.

“In five years, we could be in a 300,000-square-feet facility with 300 employees, maybe partnering with another company,” he said.