Problem Statement

Write a program where the program chooses a number between   1   and   10. A player is then prompted to enter a guess.   If the player guesses wrong,   then the prompt appears again until the guess is correct. When the player has made a successful guess the computer will issue a   "Well guessed!"   message,   and the program exits. A   conditional loop   may be used to repeat the guessing until the user is correct.

Let's start with the solution:

\newlinechar`\^^J
\edef\tagetnumber{\number\numexpr1+\pdfuniformdeviate9}%
\message{^^JI'm thinking of a number between 1 and 10, try to guess it!}%
\newif\ifnotguessed
\notguessedtrue
\loop
	\message{^^J^^JYour try: }\read -1 to \useranswer
	\ifnum\useranswer=\tagetnumber\relax
		\message{You win!^^J}\notguessedfalse
	\else
		\message{No, it's another number, try again...}%
	\fi
	\ifnotguessed
\repeat
\bye