I have created a word puzzle, and I'm interested in rating the puzzles by difficulty. There are nearly 2000 puzzles in my archive, so rating them by hand would be time-consuming and probably rather inconsistent, subjective.

Here's how the game works: <https://gist.github.com/pgblu/1fa0dccd75ecba154776>

Things I've noticed:

* 1a. The larger the ratio of known to unknown letters, the easier
* 1b. The more contiguous known letters you have, the easier
* 2. The more clue words you have (2 being the fewest), the easier
* 3. The larger the pool of 'candidate words' for any pattern, the harder
* 4. Finally, the more unusual the letters or patterns, the easier the puzzle (which is linked to #3 of course)
* 5. Having the first letter a 'known' letter makes the puzzle easier

Would anyone like to share their thoughts on designing a difficulty rating algorithm?

Easy puzzle:

* \_ I M E \_ \_ \_ \_ \_
* \_ R A C \_ \_ \_ \_ \_
* \_ R E A \_ \_ \_ \_ \_
* \_ U R N \_ \_ \_ \_ \_

Easy puzzle:

* \_ \_ \_ F F \_ \_ I
* \_ \_ \_ F F \_ \_ O
* \_ \_ \_ P H \_ \_ E
* \_ \_ \_ T U \_ \_ Y

Medium puzzle:

* C \_ \_ \_ V \_ \_ E
* F \_ \_ \_ B \_ \_ S

Hard puzzle:

* A \_ \_ \_ \_ \_
* B \_ \_ \_ \_ \_
* C \_ \_ \_ \_ \_
* D \_ \_ \_ \_ \_

Very hard puzzle:

* \_ \_ \_ \_ \_ \_ S
* \_ \_ \_ \_ \_ \_ T

solutions: 

> 
>  t...table, gra..it., .lea.ag., .erate, hideou. (the last one has more than one solution)
> 
> 
>