interface TurnI {
    Tile[] exchangeTiles(Tile[] ts);
    // hands in the tiles ts
    // result is the new tiles.

    void placeTile(int x, int y, char tile);
    // place the tile at coordinates (x,y)
    // call this method once per (non-blank) tile placed.

    void placeBlank(int x, int y, char tile);
    // place the tile at coordinates (x,y)
    // call this method once per blank placed.

    Tile[] donePlace();
    // call this method to indicate no more tiles
    // will be placed (this turn). Result is 
    // the new tiles.
}