This is probably the best implementation of the circle around enemies to kill idea,
the pixel art with the crt is done really well and it looks really nice.
I would say the difficulty curve is a bit exponential, the controls take a bit getting used to, especially the movement to mouse position being relative to its distance., and the line disappearing too quickly(maybe has that as an increase in difficulty)
The speed boost slider could use a bit of an indicator as to when it is about to deplete and when its about to refill, to give the player some wiggle room to learn escape timings and use it more carefully.
The enemies are well designed, you could add more into the game as well. different player jets maybe to add some progression as well with some in-game currency. Some more SFX and maybe a varying soundtrack as the score increase.