Thanks for playing and I’m glad you enjoyed it overall!
As for the shaded/glowing effect, I made each sprites outline start opaque and made each following layer have a lower alpha value - the inside of most objects actually was not coloured at all, instead using the background colour. I also added an extra glow horizontal effect for the player to make them stand out a bit more.
As for the difficult that’s on me, I still need more experience to find a good balance of creativity and difficulty.