The Course says nothing about what you should or shouldn't do in form (the dream). ACIM is a course in content and not form. It couldn't be otherwise, since form is an illusion anyway and content is truth.
The other thing that's important here is, that the focus on content means to ask yourself "What is the purpose?" of anything. If your purpose of "playing" inside the dream is to make you happy, through making the right moves, it would consider this a "red flag", since nothing in form will ever make you happy. The only true happiness - that is constant and eternal - lies in the non-dual nature of God. So seeking happiness, love or peace inside the dream is the basic dynamics, that keeps you sleeping.
I know, that this is the last thing our Ego wants to hear, because it's marketing campaign promises these things to be found in the world of form and through it's decisions! ACIM just wants to make us aware, that calling it "playing inside the dream" won't change the issue, as long as it's purpose is to seek things inside the dream, that are not there.
Of course, this doesn't mean, that playing inside the dream is wrong or sinful or bad, it just says, that it is insane. 😀
Yes, ACIM is radical - it will go to the core issues and this is always the content and not the form.
Please let this not prevent you from playing inside the dream @innerspace 😀Thank you for your comment and giving me the chance to take this topic even deeper! 🙏