I like your idea Pixote, but I would change the outside the top 10 scores to 2 points for a guess that ends up in 11th and 1 point for a guess that ends up in 12th. So:
Actual / Guess | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
1 | 15 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 |
2 | 13 | 15 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 |
3 | 12 | 13 | 15 | 13 | 12 | 11 | 10 | 9 | 8 | 7 |
4 | 11 | 12 | 13 | 15 | 13 | 12 | 11 | 10 | 9 | 8 |
5 | 10 | 11 | 12 | 13 | 15 | 13 | 12 | 11 | 10 | 9 |
6 | 9 | 10 | 11 | 12 | 13 | 15 | 13 | 12 | 11 | 10 |
7 | 8 | 9 | 10 | 11 | 12 | 13 | 15 | 13 | 12 | 11 |
8 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 15 | 13 | 12 |
9 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 15 | 13 |
10 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 15 |
11 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 |
12 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
Which equates to the formula:
=IF(actual = 11, 2, IF(actual = 12, 1, if(actual <= 10 ,MAX(14-ABS(actual-guess),0)*IF(ABS(actual-guess)>9,0,1)+IF(actual=guess,1,0), 0)