While bullet hell is not my strong suit, I found this quite nice to play! The core mechanic makes a lot of sense and the game is well-telegraphed so it's clear to the player what exactly is happening.
When I finished the game, unfortunately, it seemed to freeze and not allow me to return to the beginning or submit any sort of high score.
That part aside, if I were to make any changes to this game, it would be all pizazz. The player's speed being directly controlled by my keys is nice and responsive, but it feels jerky; perhaps make a fast acceleration to a maximum velocity instead to give the player character more weight. Squash and stretch on enemies can help indicate when they start moving towards you and give a sense of speed. When the enemies die, putting a little score indicator like "+1" where they died helps communicate that they are the scoring component. Small animations like this can vastly improve the feel of a game without changing the mechanics under the hood at all.
Very well done overall.