This game is pretty stylish! The colors look nice together and the bullets are easy to see, and the music fits really well - I'm not sure if you've made it yourself or used royalty-free tracks, but either way the main menu, level, game over and game completed music all add up to the style nicely!
Although, the player controls are a weaker point and could use some improvements. Specifically, the shooting part requiring you to press the mouse button key every time to shoot 1 bullet. It would be nice to add autoshot, or if the game would require shooting precision at some points (like, if you add enemies which are not supposed to be shot, e.g. Thena's mind fragments or somesuch?) - at least do it in short bursts so you don't have to spam the button, the finger gets tired and the mouse gets used up this way too, especially considering how tanky some enemies are.
Being able to control with arrow keys and shoot with the keyboard as well would be nice, arcade style games sometimes let you use z,x,c,v for shooting and other stuff, though everyone's got their own tastes. Perhaps let the player use both wasd + mouse, as well as arrow keys + z?
The game also was a bit laggy when a lot of bullets were on screen, and some bullets even disappeared before reaching the lower part of the screen. Still, these bugs can be fixed, and with some improvements the game will certainly become really cool! Again, I really like the style, especially how creepy the game over screen is, and the cuteness of Thena on the game completed screen :3