Proof there’s still room for innovation in the equity crowdfunding space yet, if Seedrs‘ claims of a first hold true. The “pan-European” equity crowdfunding platform is adding ‘convertible’ equity as an option for startups wanting to raise funding via the site, with the UK’s Future Ad Labs being the first to use the new investment mechanism.

Convertibles, commonly used in Silicon Valley and increasingly in Europe, offer the advantage of simplicity and speed, since the company’s valuation is deferred to a future date, typically when a larger VC round takes place and determined by the VCs leading the subsequent round.

Meanwhile, investors in a convertible equity (note, I’m referring to equity not debt) are offered a discount in relation to that future valuation. In the case of Future Ad Labs, it’s offering a 15 per cent discount to ‘armchair’ investors via Seedrs.

The London-based startup, which offers a revenue-generating and more human-friendly alternative to the CAPTCHA, is aiming to raise a further £400,000 through a Seedrs convertible round, adding to the $1 million in funding previously raised from a list of backers that includes Passion Capital, Balderton Capital, Ballpark Ventures, and accelerator Ignite100.

Part of that previous round also included £60,000 from 70 investors via Seedrs. In other words, Future Ad Labs has chosen to return to equity-crowdunding to raise what it sees as a bridge round before it goes out and raises a more substantial series A round; hence the choice to do it via a convertible.

Asked about the thinking behind choosing to do a convertible note through equity crowdfunding and not simply by going back to current investors, Future Ad Labs co-founder Jacques Kotze tells me the startup had a “good experience” with Seedrs before, despite being one of the first to use the platform (when I understand it had a few teething problems) and that it was “natural to return as they pioneer the use of convertibles in crowd finance.”

Kotze also says many of Future Ad Labs’ current VCs and angels will be participating in this round. “We’re not turning away from them, but we’re combining their value with the value of the crowds,” he adds. “We think it’s a wonderful opportunity for ordinary investors to invest alongside top VCs, such as Passion Capital and Ballpark Ventures, on exactly the same terms.”

Calling itself an ad tech company, Future Ad Labs’ “PlayCaptcha” ad unit lets users verify they are human, to the same end as a traditional CAPTCHA. But instead of asking users to enter a sequence of letters and numbers from a blurry image, they complete a game-like mini challenge (though, intentionally, they aren’t challenging at all), such as moving an on-screen slider in a straight-ish line to unwrap a virtual chocolate bar. These challenges are fully branded, meaning that users are engaging with well-known brands at the same time. That chocolate bar, for example, could be a KitKat.

The startup says it plans to take the same idea and use it to offer more engaging alternatives to paywalls and video loading pre-rolls which, similar to PlayCaptcha, will deliver brand engagement and an incremental revenue stream for publishers.

Future Ad Labs’ competitors include NYC-based Solve Media, and Are You A Human.