There is nothing gained from isometric perspective, but I don't think that's actually the point. Isometric view is just a different art sytle, and because I've never done it before I decided to make one now.
The mirrors are introduced at level 4, and you probably got confused on level 5. There is no better way to explain this, other than it's just isometric, and isometric can be confusing for some people.
Can you please explain the "sandbox not working" in a bit more detail? I had two people (including you) saying that it doesn't work, and three people (including me) saying that it works.
Please provide some pictures if needed, or just simply explain the problem in a little more detail so I can avoid it next time I make a game.
Thank you for playing it!