Equites is a vertically scrolling shoot'em up developed by Alpha denshi and published by Sega. It was only released in the arcades.

You control a robot which can also transform into a glider. The glider can fly over walls an obstacles, but its can only hit airborne enemies. Occasionally, an entrance to a tunnel appears. You can enter it. In a tunnel, you cannot transform into a glider, but you can use a special weapon (with limited ammo) in addition to your normal shot if you find a power-up.