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How do you come up with ideas for new games?

Hello! I want to ask you about ideas for games, what methods do you know and which you are useing ? I know for example method, to write a lot of smaller ideas on pieces of paper, and when I have 20-30 then, I try to connect one of them with another, to genereate new idea. For my the most difficult is to extend some idea, do you know some advice for me ?