Griffin has a few odd similarities to a game I reviewed a while ago, Pop Breaker: they're both Game Gear games about tanks, that are decorated (the games, not the tanks) with inconsequential pixel art of anime girls. Seperating them, however, is a much bigger difference: while Pop Breaker was a bit of a shooting/puzzle hybrid thing, Griffin is a pure shooter.
Some commendation should actually be offered to Griffin's devs, even, as they've clearly made a pretty valiant attempt at recreating the essence of contemporary arcade shooting games in 1991 on the humble Game Gear hardware. There's power-ups, screen-clearing bombs, and even a second, significantly more difficult loop that starts right after you finish the game. Between each stage, there's also some fullscreen art of your tank's female pilot after the first three stages, with the fourth and final stage being followed by the text telling you that the next loop is about to start. Frustratingly, I got right up to the final boss of the second loop before dying, so I can't tell you if there's an ending there or another loop. Sorry.
Anyway, it's a tank-based vertically scrolling shooting game. You roll up the screen, shooting enemies, avoiding bullets, and so on. Nothing really innovative on show, except for the aforementioned courage in making a game with the same design principles as then-current arcade games specifically for low-powered handheld hardware. There is one neat little graphical trick on show regarding the bosses, though. The parts of the boss you actually fight are very small, like the arms of a giant robots, or the cannons of a battleship. These aprts would be sprites, while the main, non-interactive "body" of the boss was part of the background. This meant the game could have you (appearing to) fight huge enemies, albeit huge enemies that are almost totally static. There's also one stage that only appears in the first loop where you pilot a squat, unaerodynamic-looking plane instead of a tank. This stage is the worst part of the game, having a repetitive, ugly background and incredibly boring enemy patterns. I assume the developers realised this and decided to leave it out of the second loop (but I guess they needed it to pad out the first?)
Griffin's a pretty good game. I won't say it's the best shooter on the Game Gear, as I know there's a port of Galaga 88, as well as two specially-made Aleste games, which are all probably better than it (though I haven't played any of them yet), but it is a pretty good one and definitely worth a look.