At first, it took me a bit of time to get used to the mechanic (shrinking seems to have a lot of depth), but the payoff was a sense of incredible satisfaction when using it at the right moment, and in diverse ways, I think the concept here has a lot of skill expression, the bullet patterns are also very well paced in difficulty, and the boss also has clear telegraphed patterns for the shrink skill, the hitboxes are really leniant too, the music and controls were also tight and great, so honestly, I can't say more than... Amazing job, seriously, especially solo, there is only one thing I would pick on and that was a bug that happened when I retried the 2nd time (after dying on the boss), where the stage music didn't come back when starting over.
Seriosly, great job, you nailed the classic shmup feel too.