While TMNT is the first Teenage Mutant Ninja Turtles project to take advantage of CGI animation, the movie stakes out no new ground for the franchise.

A certified phenomenon in publishing, toy manufacturing and TV cartoons - along with three live-action features in the early '90s - the green fighting machines' return to movies is a tad too conservative and calculated.

CGI delivers best on moody sets and a noirish atmosphere achieved by lighting, backgrounds and visual effects. But the characters look like plastic dolls, and the story is recycled sci-fi.

Aside from a few sequences in Latin America, TMNT sticks close to home - meaning the rooftops, sewers and back alleys of nighttime Manhattan. Its crime fighters are arrayed against the usual forces seeking the destruction of civilization, but writer-director Kevin Munroe, a CGI vet making his feature debut, focuses his main conflict within the Turtles' family.

The rift comes when the Turtles' rat sensei, Splinter (voiced by the late Mako), sends team leader Leonardo (James Arnold Taylor) away for training. When he returns, younger brother Raphael (Nolan North) is miffed about his prolonged absence. Since Leo was obeying their sensei, much of this conflict over Ninja Turtle family values feels contrived.

While Leo is away, the family falls into a kind of languor. Michelangelo (Mikey Kelley) entertains at children's birthday parties as Cowabunga Carl. Bored Donatello (Mitchell Whitfield) provides computer tech support by telephone. Only Raphael has continued crime fighting, secretly masquerading as a one-man vigilante known as The Nightwatcher.

Leo's return leads to a showdown between Leo and Raphael, while the other Turtles all but disappear from the screen. Two other crime fighters might as well disappear because the movie finds little use for them. These are April (Sarah Michelle Gellar), an archaeologist/martial artist, and baseball-wielding Casey Jones (Chris Evans), a ghost of his former crazed self. Curiously, his face is drawn so narrowly that he resembles Adrien Brody.

The villainy here is vague, almost as if it were an afterthought. At first, the enemy appears to be tech-industrialist Maximillian J. Winters (Patrick Stewart), who's assembling an army of ancient stone warriors. Then it becomes 13 monsters that slipped through a portal from another dimension 3,000 years ago. Then it's the Turtles' old nemesis Karai (Ziyi Zhang) and her mercenaries for hire, the Foot Clan.

Younger children might be baffled by the switching alliances between bad and good guys, but when the world gets saved, you don't ask too many questions.

The Turtles were created in 1984, so the real threat to its family values might be tired blood. Even CGI doesn't pump much life into these kung fu critters. Ultimately, the movie seems driven more by the need to keep a toy line and franchise alive than any creative inspiration.