[igpay]

The D20 was the first die shape I tried and I ended up just sticking with it. My reasoning was basically the same as yours - 5% intervals look better.

Agreed that 6 sided dice would not detract from the amount of strategy in the game. I think it could be cool to try a physical version of the game where you shuffle premade tiles and place them in the grid - maybe a fun game to teach kids probability :)

[livrem]

If using just 1d6 and also by including tiles that have zero neutral (i.e. no) outcomes, you get 15 possible tiles, which should be enough to build... very many different tic-tac-toe boards (I am too lazy to count, but combinations of 9 from 15 and then 9!=362880 different configurations of the tiles for each combination, although all mirrors and rotations should be excluded so in reality there are fewer than that, but still more than what you need for a (re-)playable game and probably never see a board you saw before).