I just finished this episode and the "last" puzzle was very satisfying. The ghost of Christmas future.
I actually solved it by detective work. Normally you just take everything and try everything with everything until it works. No satisfaction there. I think the first 2 ghost of the Christmas was like this.
But the last one I believe is possible only by detective work. I kept thinking and figuring things out and not once I tried anything with anything! I hear that Season 3 is more like this. That would be great.