I didn't change the shades of grass in 0.1.4 (edit: you probably mean the background grass I added?), already said I won't add music because I can't make music, that's why I added wind in the background, checkpoints just added in 0.1.5 and I'm not using any free/paid downloaded assets, I made everything myself. And also the framerate issue probably was random and got fixed with a new build and there's an official Linux build now :)
Oh cool I thought you were wanting to use it but you want to make everything yourself and that's really great!
Edit. I tried the linux build and things look fine,the menu,pause icons etc. I like the yellow glowy thing you added on the grass. But there isn't an exit button to the game? I see only pause,enable checkpoint, continue and reset progress.
Congrats on the new update! If I close the game after passing a checkpoint and relaunch it again it's supposed to start from that checkpoint not at the starting position again? Atleast that's what it used to do on the previous windows version but not now on the linux build, I start again at the starting point after exiting and relaunching.
Also right of first checkpoint, is there a level there, I see a platform?