Tactics Trainer

How are the points awarded for solving puzzles in the Tactics Trainer?  I'm a slow thinker and often will solve the puzzle correctly, yet get a negative score.  I would expect that a correct solution would always yield positive score.  This is quite discouraging to be awarded negative points for success.

we have changed it so that even partial correct answers get partial credit

my scores peaked at 1510 and have been as low as 710 in the space of two weeks.  If I log in while tired, i may as well take a 200 point rating hit.  Some are tough.

Is the trainer actually presenting me with puzzles geared toward my rating, or are they random puzzles which always raise or lower a rating by the same score?

ok. we found a REALLY big and nasty bug. jay will work on fixing it as soon as he is uncurls from a ball on the floor where he has been crying for the last hour. we'll get it fixed and then script a fix to everyone's ratings. 

I noticed something odd about the tatics trainer too. I had a rating around the 1700 and a peak rating of 1820. I did not play for a few days and then I had a massive divebomb to around a 1050. My rating today was reset to 1820. I just thought I had lost form but some of the low rating problems seemed much harder and I had to rush just to get a positive score. I'm not sure what my real rating is but I can beat computer personalities rated around 1600 .

I considered the possiblity that I am in fact rubbish and that the original problem ratings were not reflective of how easy or hard they were. I like the idea of partial credit for getting some of the moves correct. I would like the scoring system to give ratings that do not jump so wildly. You can gain/loss 70 points on just one puzzle and if your feeling tired or just having a bad day, it is possible to lose a lot of points.