Improve Algorithm for Hard puzzle

[Nanashi-lab]

Amazing game, it is a fun puzzler.

I tried about two dozen games in hard, 1 was really hard, rest were medium, and quite a few were easy. Mostly I found having queen (especially) or Rook makes it easy.

Example let's say you make one move with bishop, and the rest of the move with queen (or rook) it is much easier to solve than having complex set of moves with different pieces.

I don't have any ideas on how to do this, but I will try to make a PR for this.

[cool-mist]

There are 2 variables that determine how tough the puzzle is today

1. The puzzle generator logic here has a weighted collection of candidate pieces. The number of times a piece appears there is the probability of that piece being in the puzzle. Your observation is correct regarding Queens and Rooks making the puzzles easy, and so it only appears once or so.
2. For hard puzzles, the target number of pieces to place is 7.

You can play around with these two parameters and come up with something that you feel is tough, and then we can review.