I just finished a game of brawl where my opponent was playing a mill deck. As I had the creature card "Six" on the battlefield, cards in my graveyard had retrace during my turn (Their mill deck had gotten me to about 25 cards in my deck at this point). However, as I played on my tablet, it was impossible to cast my commander as well as my hand, seeing as the cards with retrace filled up the screen completely, leaving me with no opportunity to play the game other than attacking or ending my turn. So I had to lose the game due to not being able to cast a spell from any zone.

Maybe a rework of how zones are portrayed could be useful here, seeing as brawl is a format that can spin out of control, so the user interface should be "out of the way" of the player, lest the game become unplayable.