Twitter has purchased Lightwell, an app creation engine originally debuted two years ago by Hullabalu, an interactive storytelling startup. In its Twitter account, Lightwell said its work would focus on conversations and that its toolset, which has required a subscription, will be available for free this week as part of the purchase. Without the need to create an account, Lightwell users will be able to “layout, prototype, and export to iOS.” Lightwell also announced that it would no longer support or add new features to the toolset. Financial terms of the acquisition have not been disclosed.

VentureBeat reports that “published apps built with Lightwell won’t be affected.” Lightwell wrote on Twitter that, “we have been longtime passionate users of the product and after spending more time with the Twitter team, are incredibly energized to bring our experiences to further the mission of serving the public conversation. So, it’s fitting that we’re sharing the news with you here. With your help, we built Lightwell into one of the most powerful design-to-production tools for mobile development.”

Twitter has recently “redoubled its efforts to make conversations among users easier to follow on its platform — and less toxic.” Its prototype mobile app Twttr (which is invite-only) has new visuals “to make replies more distinguishable from strung-together tweets, along with timelines connecting replies to other users within larger threads.”

This year, Twitter debuted, in beta, color-coded and nested replies, and, in July, launched a feature in Canada “that allows users to hide replies to their tweets, requiring those who wish to see and engage with them to tap on a gray icon.”

Hullabalu developed Lightwell “to create an original story series for children called ‘The Adventures of Pan,’ which became a top seller in over 38 countries and racked up millions of downloads.” The software lets designers “create and ship animations across devices without developers having to recreate them by hand in Apple’s Xcode development environment.” The tool also offers “support for properties like ambient motion, rotation, layout constraints, and scroll views as well as screen transitions and audio mapping.”

Two years ago, TechCrunch reported that Hullabalu chief executive Suzanne Xie said that, “media companies and creative agencies looking for a simpler way to build and release apps were Lightwell’s target audiences.” The company had raised $6.5 million from SV Angel, Vayner RSE, Initialized Capital, Technicolor, and others, as well as individuals including Joanne Wilson, Scott Belsky, Carmelo Anthony and Nas.