Really cool demo, I like how you have all the tweakable settings accessible in game and using the world position texture to paint instances in the scene is a great idea. In terms of gameplay, I think having the arrows rotate with the velocity instead of always being horizontal would be the best bang for your buck in terms of gameplay improvements. I also think it would be cool to improve the grass, I think removing the shadows on the grass and having a higher density would make it look more realistic. If that causes too low performance, you could implement some level of detail optimizations where the density of the grass decreases the farther away it is from the player's view.
I tried downloading the source code but couldn't get it to run, I was getting an error with the post build event of copying dlls. Taking a look through your code I think it could use some cleaning up but not bad overall in terms of readability with your function and variable names. I think one thing to help with readability for someone new to the code would be some high level comments on your classes to give an overview of what they are for and how they are used generally. It would also be nice if the readme file had a code architecture overview. In terms of file organization, one suggestion I'd make is to separate the source code you wrote from the third party libraries your using. I usually have a src directory (for my code) and a third-party directory (for library code) at the top level of my project to have that separation.
Overall fun game and great project!