I agree with CharlesW here. That information box doesn't mention that a normal grid of pixels can also have a non 1-to-1 mapping between physical and logical pixels. Any discussion of pixels that doesn't specifically call out `window.devicePixelRatio` is not going to give people a complete understanding.
This is important. If you're rendering images/graphics with a pixel as your smallest unit then you're not going to look good on most modern devices.
Along with talking about very different issues in that aside, the author calls the px unit "a bit of a lie" when in fact CSS pixels have always been logical (not physical) pixels. My editor-hat advice is that the article would benefit from a rewrite of the px explanation, and I'd also recommend eliminating the confusing hardware pixels vs. sub-pixels distinction.
This is important. If you're rendering images/graphics with a pixel as your smallest unit then you're not going to look good on most modern devices.