The rules of "enhanced Yahtzee" follow below:
I'm used  to play sometimes some variant of Yahtzee.
You can try it pressing on the button below. (sorry for poor appearance
of my application, I've just had not enough time to fill it with various tricks. Actually my
primary goal was to learn Java)

The brief description of the main rules of yahtzee can be found in the follwing link:
http://grail.sourceforge.net/demo/yahtzee/rules.html

But I like to play a bit more sophisticated one.It differs from the conventional variant
in that that it has 52 rounds (13x4). In the conventional variant of the game you can
score you roll in any category which has not been checked yet. Here you have four
columns where you can score your roll.
    The 1st column is filled consequently from top to bottom. It means that you can score
your roll inside it to the next unchecked category down from the last checked there one.
It is started from 1 and finished at Yahtzee.
    The 2nd column is filled in arbitrary way as in conventional way. (As in the conventional
variant any unchecked to the moment category inside the column can be scored)
     The 3rd column is filled consequently from bottom to top. It means that you can score
your roll inside it to the previous unchecked category up from the last checked there one.
It is started from Yahtzee and finished at 1.
    The 4th column is filled in the most complicated way. If you decide to score there you
must accept this decision after the first roll. And after that you cannot change your mind and
score you roll in other columns unitl the round is over. If you check a category there
additional button "Fix it" appears. If you press it you score your roll there and start
the next round. If you don't press it your roll will be scored automatically after the 3rd roll
and you will start the next round.
    If you didn't decide to score your roll in this column after the 1st roll you cannot score
into this column until the next round starts.

   In addition to the description on http://grail.sourceforge.net/demo/yahtzee/rules.html
I would like to add that the objective of  the 7th (from up) category (Max)  is to obtain the
maximal score there and the objective of  the 8th (from up) category  (Min) is to obtain the
minimal score, because the result of this categories is calculated as (Max-Min) * N1, where
N1 is amount 1s in the first category of the corresponding column. This result will be added
to the total sum. It stimulates to score as many 1s in the first category as you can.

    When a round starts you are allowed to score in any unchecked category of any column
according to the rules above. You roll 3 times maximum and if you don't score your roll
after the 1st or second roll you're forced to score after the 3rd.

      I'm sorry for too short description of the rules.If anybody has questions feel free to send it
to me eugenedruy@yahoo.com