I love what you've done here. Like what MysteryMadman69 had said, you've taken flappy bird's flight mechanic and turned it into a very unique game. It was very enjoyable and I'm impressed. And especially that this was made for a game jam.
Here are some things that might help you that I've noticed
- Music would be a nice addition
- The game feels a little too static. Adding small details to your environment could completely up your game. Add swaying animations for grass and trees, and maybe even make the grass squash when you land on them. These small changes will help your game feel more alive
- The background is currently a solid color. Environment again could look more alive with a more detailed background. Maybe even change the background as you progress.
- Beginning was a little confusing without reading the description. A small tutorial could help.
I know that this is a game jam with limited time, but just some small things that could help you. Hope my feedback helps. Overall amazing game!