MOVIES BASED ON A CHILDHOOD TOY? Bah – it could never work! Um, until you remember that this is how the whole “Transformers” phenomenon got started. Nope – it doesn’t matter too much about the origin of the idea, give people what they want, and they will come. And that’s exactly the strategy behind “Battleship.” Much like its “Transformers” predecessor, it’s loud and brash, with lots of grinding gears and mammoth-sized alien-robots. These happen to be hanging out on the open seas, where Liam Neeson and his fleet stumble upon them, and the shooting begins. Brooklyn Decker nabs another film role, and she appears opposite perennial military-guy John Cena – Rihanna also makes an appearance too, although she is bizarrely absent from the trailer. And, heck, while we’re at it, we should give credits to orange fireballs and CGI. It’s opening in May, so numbers will be strong. But we think people will save their movie-going for the following week – when big ole “MiB 3” finally hits. A middling $45 million for the middling “Battleship.”