Ad-funded mobile games firm Greystripe has announced a Series C funding round of $5.5 million, led by existing investor Incubic Venture Capital, with Steamboat Ventures and Monitor Ventures chipping in.

The company says it's now generated more than 180 million downloads of games featuring its ad technology.

Meanwhile, it's also given details of how its strategy is evolving, saying it's focusing on integrating mobile advertising with existing online campaigns from big brands.

"For too long the mobile advertising world has built a silo approach to the business," says Greystripe CEO Michael Chang (pictured).

"Those days are over. It’s time to join the online advertising world and bring new value in terms of reach, targeting and interactivity."

The company thinks this approach is particularly relevant given the current recession.

Mobile-only ad campaigns may be at risk of falling victim to cutbacks in brands' spending, but if they're shifting more focus into online campaigns, then tying mobile into those is a necessary move for firms like Greystripe.

The company cites a recent campaign with HP where an online campaign was extended to mobile as an example, while another campaign for Unilever Axe was apparently funded by the brand's online ad budget.