Hi there!
Interesting little game! As you said, your background story introduces the theme, but to be fair it's not really visible when playing the game (if you don't read the description, nothing in game make you feel "oh yeah that's how the developer implemented the 'on the edge' thing").
Sprites having the same aspect ratio: YES! I really dislike when sprites are not consistent, so I'm super happy when I find a game having a proper pixel art done :)
The bullet hell at the end is really cool! Maybe you could improve that by a bit just by making the bullets more visible (outlines maybe?) because on the blue background I had sometimes trouble to keep track of them, especially the green ones.
It's overall a good game, very short but super fun.