On the plus side, Embedded programmers get about twice as much as web programmers. Switch to contracting if you want more money - around $50 per hour for web developers $30 to $75 and around $100 per hour for embedded programmers ($75 to $200). I'm not an expert on rates. This is just people I've met. It's a small sample but it makes sense. Embedded C programmers with more than 3 years of experience are damn hard to find. It's a niche market.

On the minus side, there are fewer Embedded programming jobs out there so you have to travel farther and often you can't work from home because you need to be with the hardware and often there aren't enough hardware to let you take one home. Or you need expensive debugging equipment like oscilloscopes, etc. Again I'm talking about contracting where you will have to travel to different places every time you get a new contract and they will be farther away than those web development contracts.

I recommend you stick with embedded C and if you want to learn something, learn how to use an oscilloscope, read a schematic and study some basic electronics so that when something doesn't work you can tell the Electrical Engineer exactly what is wrong instead of just saying "it's broken". This is how you get in the upper end of the salary range.

If you do switch to web programming then obviously you need to know: html, javascript, SQL. Those are the most basic and key things you need to understand.

The common, cheap, FDM printers (the ones that squirt out hot plastic from a nozzle) can print just fine upside down. So obviously they will print fine with zero gravity.

Before the web, microsoft would let you click on any keyword or function and hit the F1 key and it had great documentation hyperlinked to similar functions and with examples and it told you what .h files to include and so on. It was great. It still is somewhat decent.

Before GUI's, everything was paper doc and the languages were simpler and there were fewer of them to learn and you had to "ask someone" when you ran into problems that you normally see on stack overflow. I was one of the people that had stream of people asking questions.

Don't flame me because you think php is a bad language. I'm just saying it has the best documentation out there. It's on the web and each piece has good examples and then - most importantly - anyone can comment below for each function and feature - issues they've run into. The kind of stuff normally found on stackoverflow. I've been programming since everything was paper (the computers printed on paper only, and the documents were all on paper). I love paper docs, but online, editable, wiki like documents are the best.

Trust the crowd.