font-size
html is set to 62.5% so that all the REM measurements are based on 10px sizing. So basically 1.6rem = 16px.
Is necessary set the font-size in body tag in pixels.
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Tenetur delectus quo cumque rem atque eius, velit est ipsum, suscipit ab assumenda incidunt, pariatur eveniet nostrum blanditiis, quaerat porro reprehenderit inventore!
The next text has property font-size: 1.6rem;
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Tenetur delectus quo cumque rem atque eius, velit est ipsum, suscipit ab assumenda incidunt, pariatur eveniet nostrum blanditiis, quaerat porro reprehenderit inventore!
hidden
Makes the hidden attribute works even when an element is styled display: flex