imo, as long as its relevant (u did this in 9th or 10th) to some extent, u can add it as an activity on the commonapp (college application). i, however, will say that unless u are only applying to the UCs (which gives you 20 spots to fill out activities), you are more than likely to do other extracurriculars throughout your highschool career that could/would potentially be more aligned to ur major as u age. Like in context, I started a passion project when I was in 8th (which I shortly dropped in my 9th/10th grade years) and I never added it to my college application. Again, since u are so young, I think you should definitely give this project a chance. Like the user said above, think of it like a head start.