I’d like to make a couple of suggestion.
Used cards instead of red would be better see through/strike through or something.
The known hand, instead would require cards to be bigger (the images are really little), or yomi being yomi, could use text instead, like 3h etc.
EDIT: plus, another thing. I believe this to be a great tool for beginners, but at a high level is more dangerous than it seems. Sorting discard works perfectly for tracking what is not available anymore, and the game log shows the last revealed cards. Many, many vets play slowly already (i’ve seen many of them running out of time or going close to it often), cuz they have to keep in mind their own range, the opponent’s and calculate the payoff of every move, for knowing if they have lethal in hand or if their opponents may have it. Relying on the OHT would take even more time, hence one would run out of time so often that it would actually be a blast for the opponent (for me, at least), and to recover timer bar one should play fast, not checking the OHT and hence probably scared. jst my 2 cents