This is a simple online riddle game. There are 54 + 11 levels.
A purpose of this textbook is to introduce "riddle game" into the people who want to begin it. So this is pretty easy.
( I prepared exams at the chapter ends for the people who want harder ones though you can skip those exams. I think the last one is really hard. )

The rule is simple.
    1. Replace the answer on the URL. For example, answer.htm
      ( There are few exceptions. )
    2. The answer is lowercase alphabets only.
    3. If the answer is more than two words, remove spaces.
    4. If the answer is a person name, last name only.