The game is a shooting game, you control a fighter airplane, and Gamera follows you and assists you to defeat several enemies.
The game contains several cut-scenes with real live actors. The game can be heard in English or in Japanese, with Japanese subtitles.
The actors in the cut scenes are not very good, but it helps understanding the story: An alien invasion. You're a pilot in a UN ship that can loosely control Gamera (who flies alongside you) and command him to shoot fireballs or do his famous spinning rocket shell attack. Both of those do considerably more damage than the ship with it's laser. It's a pretty tough game, the tough part comes from some of the bigger bosses who keep firing and the way your movement is set up it's just about impossible to effectively dodge things a lot of the time.
Given that complaint though the developers made the game pretty accessible by including an easy mode.
Even the regular difficulty can be quickly mastered. It's a constantly moving rail shooter where you can flip your view from front-left-right-back and shoot in those directions.
The graphics are great for 1996 standards, the sound is great, and the music is good.
The stages are well designed, but are in a straight line. You get things like Neo-Hong-Kong, oceans, forests, and this underground level that forces you to leave Gamera behind and take a hover-bike through it, which is the only level in the game where Gamera does not participate. The game's enemies are also very well designed. You get the typical projectiles and ships that attack you, but you also get tentacles, dinosaurs, and dragon head shaped air-crafts.
During the game there is also a Gyaos invasion, with a final never seen before Neo-Gyaos, a giant Gyaos, bigger than Gamera, with two heads. The game usually recieved good reviews.