The mountain of excellent Game Boy-like retro handhelds hasn’t improved the pocketability that peaked with the Game Boy Advance SP in 2003. Cribbing from Nintendo’s square design, Anbernic’s upcoming RG Rotate has the chance to finally bring something new to this ancient form factor. After weeks of rumors and then an incoming tide of teasers, Anbernic has finally offered full details on its swiveling handheld. In short, the RG Rotate is an Android-based gaming handheld with a screen that flicks and spins up to reveal four face buttons, a D-pad, and the good old select and start keys. The top of the case includes two rows of swappable shoulder buttons. You can either get the RG Rotate in black with an ABS plastic back or a silver version that’s full CNC aluminum. This silver handheld, at 204g (0.4 pounds), will weigh more than an old-school Game Boy Advance SP, which clocked in at 142g (0.3 pounds). The black version is less hefty at 167g.…