This is a neat idea, and I quite dig the visuals here. The color palette is nicely chosen, the bird sprite is cute and the particle effects on wing flaps are neat.

The upgrade system is a funny idea, but you could probably do more with it. Right now, upgrading doesn't feel very impactful. I do like the pricing scheme, pretty elegant.

Music is fine. Some sound effects would have probably helped to give a little more feedback.

Gameplay-wise, it's flappy bird, but it works well enough. The only thing that sometimes annoyed me were collisions that felt a little unfair; I feel like that's connected to the edges of the pillars blending in with the background. Also, there's a funny glitch where the stamina meter whites out if your stamina is too high, but nothing major.

Info screen is a neat touch.