I think the point is they copyrighted these symbols as part of their branding, just like their logo, so in the context of games and game controllers

I have, but as the victim

Nope, these are bank numerals for banknotes and checks

I thought everyone disappeared and the guy from the first picture was the only person left. The speech bubble also seemed to come from him just behind the horizon

???? You know very well what I meant, be more forgiving to second-language speakers

There are decades and there are decades. Just like there are weeks (period between Monday and Sunday inclusive) and weeks (any seven consecutive days).

When you say "I'll do this next week", then you mean the next period between Monday and Sunday. When you say you'll do it in a week, it means you'll do it after exactly 7 days from now, regardless of what day is it today. Same for decades.

So in your idea there would be year +0 and year -0 before it, right?

For the same reason why 1.5 is on the right from 1 but -1.5 is on the left from -1

the idea that the year 2000 is the start of the 21st century is hurting my head.

That may be because it is not. The first century was years 1 to 100. The second was 101 to 200. The 21st is therefore 2001 to 2100.

What you're probably referring to is the "cultural century" which was considered to have started when the lead digit changed from 1 to 2. The same thing happened quite recently when some people argued 2020 was the start of a new decade (again, it wasn't)

When you consider the time as a number line, years are not points at integers (which would in some way warrant a year 0), but rather periods between them. Year 1 is the period between 0 and 1, and before that was -1 to 0, or year -1. There is no year 0, because there isn't anything between 0 and 0