The play area scaling was somewhat overwhelming but still enjoyable in retrospect. I didn't get too far, so if this happens already then ignore me, but I think you could have explored non-linear scaling, for example, making the play area twice as tall as it is wide. Graphics were really nice and I liked the visual processing of, e.g. the particle FX.
The spawns felt slightly unfair, and I think it might have been nice if these were cued in some way, for example a short warning indicator giving the spawn position and angle. I think it would be perfectly fine to not indicate what the bullet type is, as then that leaves the player with something to react to.
Great job submitting!