Wow, thanks for all your feedback! This is all greatly appreciated, thank you! :D Let me try and get through this bit-by-bit!
Thank you for the colour palette comment - I'm glad it worked! And yes, I was definitely going for a Celeste type of feel, so I'm glad you picked up on it! Thanks also for noticing the physics balance (I'm glad I got that right, phew), and yeah the music wasn't as gameboy-ish as I liked, but thanks! Also the backstory wasn't a whole lot, haha, I just thought it was a good tie in to the many adventure elements found commonly in gameboy-style games!
I've looked into some fullscreen stuff already, so thanks for that too! And yeah, I do feel the controls are a bit wack too, I just wanted to stick as closely as possible to the gameboy control panel with a D-Pad and 2 other buttons, but thanks! :D
Sorry that the UI didn't work - that reeeally isn't my strong suit. Thanks for mentioning it though, I'll try and find a fix! :D