Getting the right font-size on every mobile device

Question

In my mobile app I use kind of big fonts for example:

text

When I test it on

Answer 1

You should be using Media Queries for different device widths.

@media only screen and (max-width: 768px) {
  b {
    font-size: 20px;
  }
}

@media only screen and (max-width: 320px) {
  b {
    font-size: 10px;
  }
}

And so on...