Menacing alien machines descend on Earth, and amid all-out war, a soldier searches a building to find a frightened boy hiding in a vent.

"It’s OK," says the soldier.

"Everyone’s dying," the boy replies.

The soldier must choose: Help the boy or tell him to flee.

Though it is full of dramatic tension and realistic animation, this is not a scene from the next Hollywood blockbuster. It actually is from the coming video game, "Mass Effect 3."

Game makers are crafting more sophisticated story lines and creating characters that evolve based on their experiences within a game. It is an attempt to interest new customers and reverse a decline in video game sales as the maturing business fights for people’s attention in the face of new devices such as the iPad.

A new crop of games calls for players to make choices that go beyond selecting a weapon. Among other things, players are asked to make moral decisions that force their characters, and the game’s narrative, to evolve in different ways. Coming games such as "Bioshock Infinite" and "Star Wars: The Old Republic" tap into this vein.

These storytelling games could not come at a better time. US sales of gaming consoles and video games hit a peak in 2008, at $21.4 billion, according to market research firm NPD Group. Since then, annual sales have fallen 13 percent to $18.6 billion in 2010. So far in 2011, sales are flat compared with last year.

With the recent Supreme Court decision protecting violent games as free speech, it is more appropriate than ever for games to have more of a message.

Part of the goal of involved storytelling is to keep players occupied longer, playing out stories through to the end. Video game makers are trying to stop players from getting bored and quickly offloading games onto used game shops, which can sap sales.

The new games merge first-person shoot-em-ups with movie plot lines to develop what some in the industry are calling a new art form.

In the past, games mostly sandwiched so-called theatrical "cut scenes" between bouts of trigger-finger action. In "Grand Theft Auto IV," for instance, players are given missions on a roughly linear progression as other hoodlums call by cell phone and recruit them to participate in crimes that will elevate the player in rank. Players can follow along or ignore the story lines in favor of other pursuits, such as discovering hidden details like the giant, chained heart inside the Statue of Liberty lookalike.

Gradually, non-action scenes are becoming more central to games and the story is the focus. "Grand Theft" was a start in that direction, with two different endings depending on player choices. The new "Star Wars" game will have about 20 different endings and a billion ways to get there.

"Photographs tell stories. Movies tell stories. Songs tell stories. Games tell stories," said Ken Levine, creative director for Irrational Games.

Levine’s studio is poised to release "BioShock Infinite" next year. The shooting game confronts main character Booker with moral decisions such as saving a man from execution or putting down a horse, all the while roaming around an immersive floating world that resembles early 20th century America.

"My mom’s not going to connect to the story of ‘Mega Man 2,’" Levine said, referring to the pixelated Capcom game from the late 1980s. "But hopefully she can connect to a story like this."

These storytelling games represent yet another way the video game business is reaching out to people who have not traditionally considered themselves "gamers." Mobile games including "Angry Birds" and addicting social-network games such as "FarmVille" have gotten more women to play. Motion controllers from Microsoft, Sony and Nintendo have turned video gaming into a physical workout that appeals to young and old.

Storytelling games could appeal to those attracted to character development more than killing.

Lindsay Grace, professor of interactive media studies at Miami University, said the video game industry is trying to accomplish what Hollywood has turned into a science: entering new markets by offering a little something for everyone: a little romance, a little action, a little this and that.

"Games have started to understand this in the last four to five years, but they are later to understand that than film," he said. "Before, it was a shooting game, and that’s what you do."

Grace, who has been studying video games for seven years, believes the answer is not in more big-budget shoot-em-ups, but in independent video games pushing the boundaries of entertainment.

"From indie games to more mainstream offerings, in the next decade or so we are going to be seeing a greater diversity in subject matter," said Scott Steinberg, the chief executive of video game consulting company TechSavvy Global. "The selection of games will more closely resemble your selection of movies."

Market tracker NPD Group does not track or categorize "storytelling" games specifically, but many of the games that have had commercial success dive deeply into narrative territory. "Grand Theft Auto IV" has sold 20 million units since its record-breaking April 2008 launch. "LA Noire" was the top-selling game in the United States in May, with an estimated 899,000 units, despite an industry downturn.

A-list actors, writers and directors are increasingly participating in the industry, lending their voices, faces and ideas to the medium.

Guillermo Del Toro, the Oscar-nominated director behind such hits as "Pan’s Labyrinth" and "Hellboy," recently cut off work on the unfinished "The Hobbit" movies in part to free himself to work on video games. One of his first new projects is with game maker THQ on a future release called "Insane." Guillermo envisions the making of the game to take up eight to nine years of his creative life.

"We are in the infancy of people recognizing video games as art," Del Toro said in a recent interview.

He believes game releases will become major cultural events someday, much like big-budget movies. "In order to be a storyteller in the 21st century, we urgently need to learn to tell stories through video games," he said.

Aaron Staton, an actor from the Emmy-winning television series "Mad Men," said he signed on to play detective Cole Phelps in the epic crime game "LA Noire," to be part of the cutting-edge method of storytelling that the game explores.

Staton studied 2,200 pages of script in order to act out all the story lines that evolve from player choices. A key game mechanic is determining how the detective will react to suspects in the interrogation room. Deciding to believe or doubt them moves the story into what he describes as "its own separate reality."

Many recent games have featured actors’ voices, but in "LA Noire," their facial expressions and voices become "an important aspect of the story of the game and the game play itself," Staton said. "So I thought that it would be exciting."

Actions in these games are meant to have consequences that go beyond passing levels or gaining points. They unlock new, unexplored chapters, like a book that has dozens of endings, and provide lessons for the characters along the way.

A love triangle is expected to develop in "Mass Effect 3," but only if characters created romances in the earlier two versions.

In "Star Wars: The Old Republic," gamers can choose to play do-good Jedi Knights, evil Sith lords or six other classes of characters. Sparing an enemy’s life, for instance, will determine which direction the game heads and whether companions cooperate or betray the player later on.

Daniel Erickson, the lead writer of the "Star Wars" game, said the amount of storytelling content was unprecedented. The studio behind it, BioWare, created more than 10,000 characters to talk to and used voices from more than 1,000 actors.

The alternate paths amount to more than 60 "Star Wars" novels worth of content in a script that, if read completely, would last longer than the entire 86-episode run of the HBO television show "The Sopranos," which would take three days without sleep.

"BioWare is a lot closer in structure to a continuing ongoing TV series studio when it comes to the writing department than it is to a classic game design studio," Erickson said. "It is story that drives everything."

In this screen shot provided by Electronic Arts Inc., a scene from Mass Effect 3, is shown. (AP Photo/Electronic Arts Inc.).