This question sparked a thought in me.
To me, the author is not doing this for exercise (not tagged with reinventing-the-wheel and no mention of the sort) so I assume it is done for production. I happen to have some experience with LibGDX which the author uses, enough to know that the library can do most of the functionality they have spend time implementing out of the box, rendering their code mostly redundant.
Is it an acceptable review to say (albeit more politely):
Hey, you're doing it wrong! Trash all the code you've written and use the library functions you already have. Look at these classes and here's how you do it...
I posted originally as a comment because I didn't think it was an actual review but then I was requested to post that as an answer so I did (somewhat reluctantly).