How secure is 256 bit security?

"It uses 256-bit encryption" sounds like marketing until 3Blue1Brown makes the number physical. In about five minutes Grant Sanderson asks how long guessing and checking would take, then stacks up imaginary computers, planets and galaxies working on the problem until the answer stops being a number you can picture. There is no math to follow beyond multiplying by four billion again and again, and the animation does the persuading. It is the reason engineers shrug at brute-force attacks and worry about stolen passwords instead.