First off, this is an extremely well-designed card game in its own right. The rules are simple, but it takes a lot of forethought to play well, and forces you to balance several different considerations at once. Unlike normal solitaire, about 98% of deals are theoretically winnable, so it’s normally your fault if you get stuck.
The UI is very simple. I like that there’s no undo button, because it forces you to think ahead more. My only wish is that you could toggle the sound. If you’re wearing headphones, you can’t turn off the music.