Hello, some feedback for you :)
I like the design of the game and the animation of the character. The crystals look a little out of place though. Also, the game is far too easy. I would suggestion removing the double jump and making the crystals spawn a lot quicker.
A simple UI but it works. If you really wanted to add some final polish to the game, add some sound effects and music. Keep up the good work :)
If you want me to play test another game you release in the future, just get in touch. You can contact me on Itch or join my discord and contact me on their. My discord link is on my profile page.