20 Time Project Idea

I really want to pursue a project on writing. I've been writing stories since I was five years old and this project is a great opportunity for me to do some writing. A project on writing could help me for my future because I want to be an author so I think doing a writing based project could beneficial for me. None of the other ideas on the discussion really appealed to me so I think I'm going to write a science fiction novel. I don't want the novel to be one measly 200 page book, but something along the lines of 400 pages or something. I've only completed one novel in my life and it was only 330 pages so I want to see if I can push myself to write a better one. In order to do this, though, I'm going to have to make myself be more specific with descriptions as well as make it the length I'm hoping to make it. Now I've just got to think of a plot for it and then create the characters.