Tile and Color enum values in the code are different from the paper

I found that the values of Tile and Color in `core/constants` are different from the ones shown in Table 1 in the paper. E.g., in the code, `BALL` has a value of 3, but the paper says `FLOOR` is 3. 

I understand that we should follow the code, but it would be great if the paper can also get updated to avoid confusions.