Split out 'blanks function from add-random.
Add line separator in 'print-board for readability.
Allow game to go past 2048 (wishful thinking).
Add 'auto-play and two players.

'random-player moves randomly and probably has a mode of 128.

'monty-player, with either 'empties or 'games-score as the criteria,
has a mode of 1024.

I've not seen either hit 2048.