It is my opinion that “TMNT” is as good a movie about teenage mutant ninja turtles as there can possibly be. The protagonists are mutated turtles who have learned martial arts, have grown to the size of adult humans, and have learned English. I really think B- is as good as you’re going to get with this premise.

“TMNT” is aimed at two audiences: 12-year-old boys, and grown men who loved the Teenage Mutant Ninja Turtles in the early 1990s, when they were 12-year-old boys. I did not pay attention to the TMNT phenomenon until much later, when I watched the 1990 feature film and was impressed with how bad it was. What I called “bad,” though — lame jokes, hole-filled plot, clownish acting, etc. — was apparently what many fans LIKED about it. So take it for what it’s worth when I say the new “TMNT” film is a lot like its predecessors.

One way it’s better, however, is that it’s animated. It never made sense to make live-action films about characters who never looked remotely convincing when played by actors in rubber suits. “Teenage Mutant Ninja Turtles” began life as a comic book, then became an animated TV series; it should have stayed animated. You accept a lot more simplicity, silliness, and just plain dumbness with a cartoon than you do with live-action.

The new film is computer animated, and it looks fantastic. The movement is sleek and fluid, nearly as much so as in a Pixar film. Writer/director Kevin Munroe (his first feature film) and his animators make full use of the technology to give “TMNT” action sequences and visual effects that would be expensive or impossible with real actors and sets.

The story picks up a few years after the last film left off, which means our heroes probably aren’t even teenagers anymore, though they’re definitely still mutant ninja turtles. They all look the same, so you have to memorize which one has which color headband. Leonardo (blue headband, voice of James Arnold Taylor) has been living in a jungle for a year, sent by Splinter (Mako Iwamatsu) for some training. Back home in New York, Donatello (purple, Mitchell Whitfield) and Michelangelo (orange, Mikey Kelley) are finding non-ninja ways of making a living, while Raphael (red, Nolan North) has assumed de facto leadership of the group and spends his nights as an anonymous crime-fighter called the Nightwatcher.

Then Leonardo comes home, and just in time: A sinister man named Max Winters (Patrick Stewart) is using magic to reanimate ancient statues, which he sends out to collect a batch of ugly monsters, for which he has additional nefarious purposes in mind. Do not trust a man who brings statues to life, and especially do not trust him if he uses the statues as monster-fetchers. You can take that one to the bank. But before the turtles can fight Max Winters and his evil horde, they must repair the rift that runs among themselves. Only as a united team can they save the day.

The action scenes are lively enough, and taken for what it is — a cartoon about crime-fighting reptiles — it’s fine as Saturday-matinee entertainment. The turtles still make corny semi-jokes like, “Why skate a half-pipe when you can skate a sewer pipe?!,” and human friends April (Sarah Michelle Gellar) and Casey (Chris Evans) are still on hand to get in the way. If you liked the previous TMNT films, then I can’t imagine why you wouldn’t like this one, too.

B- (1 hr., 27 min.; PG, cartoon violence.)