Thanks! For PDF form filling, I use the APIs that pdf-lib [0] exposes. That includes text fields, checkboxes, radio buttons, dropdowns and options lists. Give it a try and let me know if you find a type of form field that's missing.
One idea was a workout mobile app with achievements (badges) - Duo Lingo for workouts. You pick a ready-made workout plan (or create your own) and it gives you badges to reward your progress and encourage you to keep going. What concerns me is that the market is over saturated - a quick search in Google Play shows hundreds of results for workout apps.
Another idea was improving the renting experience in London (where I'm based). There are so many new flat listings here that it's hard to find the ones you like. My idea is to crawl over the more popular agencies' websites and organize the listing information neatly with extra customizable filters, such as "1 mile away from a tube station" or "bedroom that is at least X sq.m." (for the ones that have an included floor plan). I haven't actually tried out that idea yet, and it would definitely solve a problem all my friends and I are having - we all go through a miserable experience in finding a flat. However, one problem would be that some of the agencies' ToS prohibit crawling.
I also had an idea about a Citymapper-like tourist guide mobile app, but with the pandemic, that won't be relevant anytime soon.
In another comment on this thread they explained that space and time are parts of the same vector, <x, y, z, t>, with velocity being the speed of light. Here you mentioned time is frozen at the black hole event horizon - does this have to do with the theory that we can use black holes as "portals" to distant parts of the galaxy? So if time is 0 and we have <x, y, z, 0>, does this mean we travel at the speed of light?
1) I'm a software engineer, have a good foundation in mathematics and physics. I could use a refresher on the electrical engineering area of physics though.
2) What I want to do - for starters, small hobbyist projects like playing with sensors, displays, etc. My end goal is to be able to design cool IoT projects, such as smart security cameras, and sell them.
3) I can dedicate 1-2 hours per day. I don't expect to have the equivalent of a Bachelor's degree any time soon, but am happy with any kind of pace.