San Rafael-based adventure-game company Wunderverse Interactive plans on June 4 to launch its new application for the iPad that allows players to create and share their own dramatic tales.

To inspire new users, the software will have a few sample stories already written in several genres: post-apocalyptic future; 1940s crime noir; ancient-ruins archaeology; atomic space and medieval. Players whose imaginations soar can invent their own fiction then share it with friends, who can make plot choices along their game paths. The sample stories are not long, requiring perhaps half an hour to complete. As authors build more complex stories, they could potentially take hours or days to follow.

Wunderverse joins a bustling hub of game development companies located in Marin County, including Telltale Games and Vector Unit in San Rafael; FreeRange Games in Sausalito; and 2K Games and Toys for Bob in Novato. Autumn Moon Entertainment is in Petaluma.

Co-founder Shawn McKee, who developed the software and helped fund the enterprise, started the business in 2014 with partner David Mullin, who is responsible for writing and illustrations that make up story content. The choose-your-own content is flexible, adapted to players’ whims as they move through stories. Some players may choose to become authors in the games.

“At some point in the story, you are presented with a choice,” McKee said. “You can base the outcomes of your stories on a lot of things” depending on what plot twists have already occurred. “You don’t know what’s going to happen until you have made your choices.”

The game features interactivity.

“You might come across an old woman sitting in front of a vault,” McKee said. “You can talk to her, ask her” if she knows how to open the vault. The story options “are choices the author has set up for you. You could have her be somebody who becomes adversarial. You can trigger those actions — make her adversarial — by something you say to her. The author sets up that outcome.”

The app, available through Apple’s App Store for $3.99, is aimed at players age 12 and above.

Younger players might not have the cognitive skills needed to play, McKee said, because some logic is required, especially to originate stories. The “voice” of the narrative is often second-person, as in: “You hurl a ball of fire at the approaching robot.”

Each story is expected to cost $0.99 to $1.99. The founders “hope that thousands of people buy that story for a dollar,” McKee said.

In attempting to gauge the potential market size, McKee estimated the number of iPads already sold: 200 million. “We’re trying to create a user base,” he said. Eventually he plans to adapt the software to iPhones, of which there are nearly 500 million.

“We are trying to give everybody the ability to create their own stories,” McKee said. “We have big plans to move forward.”

Mullin is working with traditional fiction authors to adapt their stories to the Wunderverse format, according to McKee. “We’re going to come out with a whole line of complete stories that players can purchase in addition to their own stories,” McKee said.

“We’re trying to bring back some of that exploration and wonder and imagination” that children used to find in books, McKee said. The process of inventing stories “sparks the imagination,” he said.

The story builder, which requires no code-writing capability, allows user-authors to add art along with their plot elements. Stories can include events, such as entering an area or realm.

“You as the author can react to that event,” McKee said, “by providing outcomes. One outcome of an event might be that they (characters) fall into a pit and go into a completely different area of the story.”

The third story element is conditions. “One condition might be whether they are carrying an item,” McKee said. “You might not let them (characters) see what’s in a room if they’re not carrying a lantern.”

Authors can import images such as photos and illustrations to flesh out their stories; all the elements are stored on the iPad. Once Wunderverse users decide to share their stories, the art elements are optimized and packaged then sent to Apple’s iCloud, available for other players to download.

“You download that complete story with all the artwork,” McKee said.

He plans to expand the app to include multi-player real-time uses. “We’ll be doing some tricky, on-the-fly sharing stuff,” he said.

“Kids love it,” McKee said of Wunderverse. “We wanted to drop the age range down lower.”

Mullin has two girls, ages 13 and 17. “They took to it immediately,” McKee said. “They feel that our genres are a little bit too male.”

“I have used them as our beta testers,” Mullin said of his daughters. “They gave us ideas for other genres such as young-adult and science fiction. My youngest daughter is into My Little Pony,” a Hasbro franchise marketed primarily to girls.

So far the app is only available for an iPad.

In addition to McKee and Mullin, Wunderverse has a comic illustrator and a musician to compose original music, along with a marketing colleague. The illustrator has produced black-and-white line art for the genres due to be available on June 4 for the launch, Mullin said.

“The plan is to offer clip-art,” he said, with a library of images that players and authors using the app could bring into their stories.

The fledgling company could face some issues in its Wunderverse name, which resembles the German “Wunderkind,” meaning a child prodigy. “We like the name and thought it was appropriate,” McKee said.

Another company, started about five years ago in Burbank, California, used the name Wonderverse and did social gaming and mobile gaming. On May 28, a click on the Wonderverse.com URL went to a blank page. A Wonderverse.tv URL went to a live website.

“It is a marketing issue,” McKee said. “It’s something we noticed. I’m a developer and Dave’s a writer. It’s not really our realm.” A child user may struggle to remember the German spelling for Wunderverse.

McKee, who started writing code in 1993, worked as a freelance developer for Blue Rocket, an iOS and mobile development consultancy in San Francisco, building apps for Zinio digital magazine as well as Remodelista’s iPad and iPhone apps.

Mullin, who has worked on several novels and screenplays, used to own a portrait photography business. He attended University of California, Davis, where he earned a degree in history and psychology, and also learned HTML, CSS and JavaScript.

“My kids are on their phones and iPads constantly,” Mullin said. “They also like to read and to play games. This is converging all that into one space. I loved those choose-your-own-adventure books when I was a kid.” He also played Dungeons & Dragons, a fantasy tabletop role-playing game.

Mullin figures that about 20 percent of Wunderverse’s market will be people who want to author their own stories, and that 80 percent will simply buy stories created by their friends or the company.