Once upon a time, I endured a performance of an original play at a local theater starring a precocious 8-year-old girl who had more lines than Hamlet. I don’t recall the plot, the jokes or even the basic premise. All I remember is thinking, “Phew! How the heck did that kid memorize all those lines?” It was quite a remarkable feat, and most of us in the audience were duly impressed.

We were not, however, entertained.

There’s really no way around that. As a general rule, an 8-year-old kid doesn’t have the chops to carry an entire production on his or her back. That little girl certainly gave it the old college try, but, as bright and talented as she was, her flat line delivery was just one notch above what Siri would sound like if she had the lead in “My Fair Lady.” You could understand most of the words, but you didn’t enjoy listening to them.

Which brings us, of course, to the basic problem with the upcoming “Ender’s Game” movie.

I’ve wanted to see a film adaptation of Orson Scott Card’s sci-fi masterpiece since I first read it in 1989. Back then, I feared that two looming obstacles would prevent such a project from ever coming to fruition. In the first place, I lamented that special effects would not evolve to the point necessary to adequately bring the battle school scenes to life.

Clearly, time and technology have removed that particular roadblock. The recently released trailer for the movie shows that great care has gone in to making those sequences as compelling and lifelike as possible.

Unfortunately, the second impediment to a successful “Ender’s Game” adaptation cannot be so easily overcome.

“Ender’s Game” tells the story of children who are recruited to lead the human race in battle against hordes of bug-like alien conquerors. Earth’s leaders determine that the invaders can anticipate our every move, so they turn to young children to add innovation and unpredictability to the mix.

And when I say young children, I mean young children. Ender Wiggin, the story’s protagonist, is only 6 years old when the novel begins. He is at the center of nearly every scene, and he’s forced to struggle with monumental moral decisions that would flummox a man 10 times his age. So how the heck do you saddle a performer with that kind of responsibility when it’s been less than a decade since they were still in diapers?

You don’t. Or, at least, they didn’t.

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In the movie, Ender is being portrayed by Asa Butterfield, a bright young actor who, while perhaps talented enough for the role, isn’t anywhere near young enough. He’s 16 years old, fully a decade older than the character he’s portraying is supposed to be. In two years, he’ll be old enough to join the real military, so when Harrison Ford intones in the movie’s trailer that Butterfield’s character is a “new kind of soldier,” it doesn’t seem all that impressive. Oh, sure, he’s a new kind of soldier — one that’s just a hair younger than the old kind. It just doesn’t work.

Or maybe it does. I haven’t seen the movie yet, and I’m certain I will see it, regardless of the kind of reviews it gets. Perhaps they’ve figured out how to compensate for the age shift, and maybe it will turn out to be the Ender movie so many of us have dreamed about for so many years.

But watching the trailer, I can’t help feeling like it’s missing a core element of what made the original story so special.

Jim Bennett is a recovering actor, theater producer and politico, and he writes about pop culture and politics at his blog, stallioncornell.com.