[kittoes]

Unless you're supremely lucky, this kind of stuff is a hobby. One wishes that weren't the case, but capitalism is what it is...

I'd encourage you to generally ignore whether something has direct value or not because that's not how knowledge works. For example, I once spent well over a month implementing the NthWeekday function using nothing but basic arithmetic operations. This would allow us to calculate all federal holidays for a given year at runtime instead of precalculating the values and storing them in a table (which I hated, because it meant that someone had to maintain that table). This hyper-specific problem has near-zero direct value, but it was THE project that sparked my passion for maths.