Because of all the various platforms and screens in use today, responsive typography is a critical component of good web design. Variable fonts (formerly known as Open Type) can change width, height, and/or slant. Instead of being limited to only certain weights, or using cumbersome width measurements that are not responsive, developers can apply the font-optical-sizing property to variable fonts to ensure a smooth experience no matter the size of the viewport. With a little extra css trickery, they can be animated into an impressive display.