I liked it, simple and neat. Game looked like something that could have been released on gameboy, so it's fully relevant to the theme.
Graphics weren't blowing me out of the water but they were good at showing the barren wasteland. The concepts for the few monsters I saw was also really nice and they fit the theme of the game.
Gameplay was simple, but there were places where you could feel game needed more time and polish. The starting sequence of some voice or horse talking to me was confusing and at random times at the beginning but also after getting the armor I was not able to move to the right, I would have for some reason move left a bit before going forward. Also it feels weird that the projectiles kill you only if you jump on them but will only push you away when they come at you. All of those things made me unable to go too far into the level, and I might just be a bit nitpicky, but fluid gameplay is always most important to me.
Audio was simple, but it felt right for the gameboy game.
Not being an avid player of castlevania or Ghosts and Goblins I can't really say how well does this game use these game elements or if at all.
All in all, there places for improvement, but game itself feels solid and I would love to see where it goes in the future. If I had to rate it I would give it 3/5.