The art is not consistance. I'm not a pixel artist but mixing pixels are challenging task to do and need to keep in mind. The bg are fine but dont go well with pixel. The music is too repetitive for a repetitive gameplay, need to have a nicer loop. There are no sounds feedback. The UI could be done nicer.
About the gameplay experience. I dont know to make the bird spin if I didnt read the instruction. The pipe does not look like a surface to make the bird spin > a huge deal to give the player the idea that it can make the bird spin.
The bird spin does not affect the game play. If I were a game designer I would make that if the bird spin more > harder to control but with higher payoff as in points. Also when gen a point there could be a sound for it for gameplay feedback maybe in the first 1 to 10 and then 15 then 20 for not getting repetitive easily.
Keep it going, practice and improving!