It's funny, I reached the UFO during one of my vey first tries then rarely went even half as far. I think I got really lucky regarding speed potions during that one run. I got back to it only a lot of runs later, then died just after it disappeared, did one more run where I had some time to see what happens after it disappeared again, so I guess it's more or less the end of the game or the beginning of a new loop where you'll quickly die. It's fine whatever it is.
Grid-based movement is a cool implementation of theme (I won't say otherwise when the first part of my limited movement level precisely limits you to walk through a grid ;) ), yet I only moderately like the slow movement, I guess it's fine for the game length but could get annoying if it lasted longer. It's a game where you navigate between bullets which is why we're here and I think the difficulty is right on point so as a result the game is fun, I also particularly like the music.
Good job, thanks for sharing.