That's a cool game! For some reason the controls felt completely backwards to me and took some getting used to (i kept wanting to move with WASD and shoot with arrow keys). It reminds me a lot of that cowboy arcade game that you play in the bar in Stardew Valley. Lots of fun! I think you did a good job sticking to a palette and choosing some cool music which goes a long way towards making an enjoyable experience, though I would have liked some sound effects and a few more polish details (screen shake and particle effects would really have worked well here I think.) Music is pretty cool, I'm going to have to check out the artist!
I read through your post, the submission info, and the other reviews and your comments and still couldn't figure out the relation to the theme on this one, but overall I think it's a good game and a job well done.