Solitaire Chess Puzzle Generator

Goal: Generate 'hard' puzzles.

Heuristics of current algorithm

1. About 6-7 pieces on the board.
2. Select pieces to place based on its weight. 3. Eg: Queen is too powerful, so it has lower weightage. 4. Eg: Knights are confusing. More knights.

Example puzzles generated

N...
P.B.
.R..
..KP

R...
..P.
..B.
.KNN

.PN.
P...
K..P
.R..

..PK
...R
P..P
B..N