I recommend Unity.

Unity is not that difficult if you clearly understand the Template Method pattern. The difficult part is that students often struggle at a different point than expected.

That said, if not Unity, GameMaker is also a good option.

That’s spot on.

However, it’s been a while since I really dug into Unity, so things might be different now with tools like Codex or Claude Code (without suggesting we just resort to "Vibe Coding," of course). If you have a way to consult someone—or something—about the hurdles you can't clear on your own, Unity remains useful in terms of the sheer breadth of what you can achieve.