The `vw` unit equals one percent of the current browser viewport’s width. Unlike a percentage, it measures against the whole viewport rather than an element’s parent. section 14.3
Use viewport units when sizing should respond to the screen itself:
- Use `vw` for horizontal measures such as width, padding, or margins when they should scale with viewport width. section 14.11
- Compare `vw` with `vh`, `vmin`, and `vmax`, which scale from viewport height or the smaller or larger viewport dimension. section 14.3
A quick viewport calculation
On a 1,600-pixel-wide viewport, `1vw` equals 16 pixels, so a value expressed in `vw` grows or shrinks with the browser width. section 14.3
