molten-type

A set of modular scales for fluid typography that responds to viewport changes. It combines the relationship between a text's font size, its line height and its line length. Instead of adjusting just the font size on a breakpoint by breakpoint basis, a molten type will adjust all three for every viewport size, as the viewport changes.

So what is a modular scale? To put it simply, a modular type scale is a list of font sizes that work well together because they increase by the same ratio. We start with a base font size and multiply it by the ratio to obtain the font sizes we can then use in our CSS.

For example, having a base size of 16px and a ratio of 1.5 will yeild us a list of 16px, 24px, 36px, 54px, 81px, etc.

In addition to changing the font size based on a ratio, molten type will also adjust the font's line height and, if a variable font is used, its font weight. It all happens automatically for each viewport width, and each viewport width will take into account the type scale ratio.

molten type demo

Out of the box, molten type has the following type scales:

Name	Ratio	File
Base	1.000	`index.css`
Minor Second	1.067	`minor-second.css`
Major Second	1.125	`major-second.css`
Minor Third	1.200	`minor-third.css`
Major Third	1.250	`major-third.css`
Perfect Fourth	1.333	`perfect-fourth.css`
Augmented Fourth	1.414	`augmented-fourth.css`
Perfect Fifth	1.500	`perfect-fifth.css`
Golden Ratio	1.618	`golden-ratio.css`

Additionally, you can set the ratio yourself by adding the index.css file and overwriting the root CSS property for --type-scale.

<link rel="stylesheet" href="node_modules/molten-type/index.css" />
<style>
  :root {
    --type-scale: 0.8;
  }
</style>

Usage

First install the package from npm:

npm install --save molten-type

Or with yarn

yarn add molten-type

Then link to the stylesheet you want to use:

<link rel="stylesheet" href="node_modules/molten-type/major-third.css" />

Or use it in your SPA or similar. For example, in a Gatsby website, in gatsby-browser.js:

import 'molten-type/major-third.css';

Browser support

If you still have to care about IE11 and below, you cannot use CSS variables. You also need to support calc(), which is a bit flaky in IE11 and below, as well Safari and iOS Safari 6 and 7 (which won't support viewport units in calc()). Sad face!