This was a lovely game (thank you for giving me the opportunity to proof it)!
The usage of the visuals is perfect for O2A2, as there really is no need for anything else - just a man, rolling his boulder up the hill (and indeed, the fact that the visual stays the same, even after the man rolls the boulder up and down multiple times, emphasizes the futility and monotony of his task). The little animations are very immersive, and I liked the choice to not include BGM, as it really allowed you to focus on the game itself.
===SPOILERS===
The entire game is very metaphorical. While it can be applied to Sisphyus' task, literally pushing the boulder up the hill, it could also be applied to some a person's mental state - their attempts to change, and how they fail to change in spite of their desire. I like how the struggle is framed not as an external one, but an internal one - a struggle against the self. In the game, Sisyphus feels discouraged, troubled, even as he continues to push the boulder up the hill - until he finally can't do it anymore, and the boulder falls back down. However, at the end, Sisyphus decides to continue pushing the boulder up the hill, despite the meaninglessness of it all, deciding that he will create his own meaning - and that his growth is meaning in and of itself, that this is work that he has created for himself.
I like this reframing of the myth - Sisyphus is not forced by the gods to push the boulder up the hill. Instead, it is something he decides to do for himself - and despite knowing that it will fall back down, that he'll revert back to his toxic patterns, he persists. His happy ending is to accept the futility of his task and to appreciate the act itself, rather than to "succeed." It's an appropriate message that's pretty universal - indeed, many things in life are "meaningless," and you decide to do them because they are personally meaningful to you. It's an uplifting message, and a realistic take on what it means to "heal."
Great work on the game by the dev!!