This game combines vertical, horizontal and perspective shooter. However, it is neither of them. At the end it can't achieve the precision of 2d shooters, nor the inmersion of the 3d ones.
When the game gives the idea of highlighting hitboxes you know there is something wrong.
The main problem is the bullets. its color. the enemy bullets mix with the backgroundand the effects. you have to force your sight to see them. This is especially anoying on the 5th and final stage when the bosses start shooting voleys of small purple-grayish bullets which are the same color as the background.
Then comes the perspective. On the same stage, the game changes the perspective like 10 times, leaving you confused and dizzy and at the verge of a seizure. And it gets even worse when you combine this with the bullets problem. You don't know what's on the same plane as you and can kill you and what is over or under you.
Come on, I am trying to play! If I'd want to see spaceships shooting at each other in some weird angles I'd watch some mecha anime.