Really cool idea! So cool that I really wanted to provide a ton of feedback, so sorry for the wall of text here, haha.
Feedback and thoughts:
I'd make the tutorial something the player can click through versus being set on a timer (unless I missed something, which is very possible!). I loaded the game, got side tracked, and then it started before I could read it and had to refresh the page. It is a lot of text, but it's also a very unique concept so I can understand the need to explain the way you did. I had to read the tutorial a second time to realize that I needed to fly through clues to choose one (my knee jerk reaction was to click them with the mouse)
I absolutely LOVED the 3d shatter effect, gave me big Symphony of the Night vibes! The bullet spread patterns, which look awesome btw, are a bit too tight to really navigate around - especially since a portion of the screen has the clues, which you don't want to hit by accident, and they come from all sides instead of simply from the top / one side like a more traditional bullet hell game.
I think a way to improve this would be to have the bullet generators appear in "waves" from the top with more predictable patterns to navigate.
Another possibility is to allow the player to shoot and destroy them, and have the enemies then drop the green orbs to reveal the painting. In between waves of bullet hell, spawn a row of the guesses and have the player fly into one....then repeat a wave or two of enemies.
The bullet time is a great idea - I would recommend lowering the pitch of the in game music, zooming in the camera a bit, and adding a touch of vignette to really make that effect punch. My hardware acceleration was already on, but the suggestion on the page was a nice touch! :)
Overall I think this was really neat, and I'd love to see the concept played with more as it is truly unique. I'd would ABOSLUTELY play a more traditional "shmup" with this kind of idea! Great work!