Agree. I wouldn't change a thing. There are so, so many unscrambling words games. If someone just wants to casually unscramble words, they can find something more to their taste.
As implemented: There is a clear "game over". You did as well as you could; try again tomorrow. That's great. The length/difficulty gets harder as you go on, so getting to 18 is a true challenge. Also great. The letters are in the order they are in, no reshuffling. This is also great. You can't just spam reshuffle until you see it; you have to make do with what you got.