The 'Ray Series' is a Taito developed sci-fi shoot em up series. The series is known for its use of literal depth in its gameplay. While your ship moves in (and is locked to) a normal 2D plane like many other similar titles of the genre, the use of multiple enemy lock-on targeting a la Panzer Dragoon along with enemies that move in and out of the players plane brings a certain twist to this particular style of game, a feature that has existed even in the first 2D entry.
Unfortunately, due to licensing issues across multiple territories the series has not been completely seamless in terms of naming conventions. The first entry in the series, RayForce was renamed Galactic Attack in North America and GunLock in Europe. Even in Japan the game was renamed Layer Section when it came to home consoles. This naming convention continued somewhat with RayStorm which while unchanged in North America would be known as Layer Section II in Japan. RayCrisis was the last Ray title developed and while its name did not change the game is actually a prequel to the original RayForce, taking place inside of a virtual reality.