The situation: I've a sister over a decade my junior, 9th grade, who is looking for a science fair project. Neither the teacher's suggestions nor ideas she found via internet search excited her, so we were kicking ideas around. Based on her desires (something different / unique) and knowledge (beginner Perl programmer, just basic operations and ideas like variables, arithmatic, etc.) I suggested a computer science project.

So we popped online and looked at ideas, but the wall we are hitting is that neither of us is really sure what a good project is, in terms of scope. What is too much work, and what too little, for a beginner? Ideas so far that piqued her interest:

• Something with board games and AI. Perfect play with a trivial game seems too modest a project, but even a small sub-problem of a more difficult game seems daunting. Regardless, ideas along this line seemed most exciting to her, out of the options we looked at.
• Author identification via text analysis.
• Encryption. Probably something involving frequency analysis to break substitution ciphers.

Question number one to the monks: Do you think we're in the difficulty ballpark here, given limited Perl experience and the 9th grade level? The school doesn't really give guidelines as to how "big" the project should be, but based on looking around at the science fair last year I'd guess the median to be around 100ish student-hours. Well, the median of the not "slapped-together-last-night" projects.

Also, if you've other ideas, please share them. I think our best bet might be finding a difficulty appropriate board game / AI problem, but she seems open to anything interesting.

Update: Thank you to everyone who has provided perspective/ideas. Going to point my sister to this thread and see what she thinks.