# Scrabble rack observation with MuZero

Currently I'm trying to implement Scrabble with MuZero.

The $$15 \times 15$$ game board observation (as input) is of size $$27 \times15 \times15$$ (26 letters + 1 wildcard) with a value of 0 or 1.

However I'm having difficulties finding a suitable way to encode the player's rack of letters (Always 7 letters on the rack).

The available tiles are: 26 letters $$(A-Z)$$ and 1 wildcard.

A rack can also contain multiple tiles of the same letter.

Example: rack of player 1 is $$[A,A,C,E,T,T,H] -> A:2x, C:1x, E:1x, T:2x, H:1x$$

How can I represent a rack of tiles as a $$(? \times)15 \times15$$ (or other board size) matrix ?