Pretty fun game, I enjoyed how tactile the physics-based controls felt, although the diving felt a bit too fast, too abrupt. Two things I'd change:
1. Buying the heart pickup upgrade made the game too easy, I would recommend starting with smaller, less impactful upgrades or multi-tiered versions of them.
2. When going fast some obstacles appear after I already jumped and have no control over my trajectory, so if a flock of seagulls jumps when I'm already jumping I can't avoid them.
Still, I had a lot of fun, got to about 5000 meters and bought all the upgrades.