Simplicity is beauty, independency promotes creativity.

A wit-besteading and will-demanding cute little numerical game，who had always wanted to bring you more fun with his expert knowledge. The game, with a concise and clean operation interface, an permissive and emanative playing method, and four steady while freaky numbers, presents you with continual joy out of exploration and adventure, both good for your subtle EQ and brittle IQ. You think you sharp body and mind? Then, why not give it a try, and prove it. You are immortal here till the mystery is unfurled, and you would be immortal if you are brilliant enough to unfold the problem within five steps. Work it out!

"Somewhat strange and straightforward, though it might be a bit addictive for a short while. The game picks a random 4-digit number, where all the digits differ, which you try to guess. It tells you if you have any numbers correct and whether they are in the right digit, but not which number(s) are correct or which digit."
-- Matheme0, from app review.

If you have any advices, including advices on features, you are welcomed to contact me and give me a piece of your mind. If you are a programmer too, I can even share the source code of this app with you.