I'm glad you enjoyed it! 100% agree on the undo button -- I took a stab at it, and it was buggy af (lots of edge cases), but I think it's more-or-less necessary.
I like encouraging deck tracking, but I think I'll give players visibility into like, their total deck contents. That still keeps the tactical edge of tracking where your good cards are, but it makes it a bit more accessible I think.
I definitely want to add duration cards or something like it! Probably something to unlock after the first run.