Software projects are usually 90% done in 1% of total time taken. And if you just solve the problem with duct tape eg. a shell script, like piping stdin to a file, or contenteditable=true in HTML, you would have a very basic word program, and if you take that route you will probably have the essential features done over a weekend. But going from that to a full Office clone would take years. The real challenge in development though is to solve real problems, eg not make solutions looking for a problem, and not implement new features ( implementing only features that solve real problems).