How to reduce default margin/padding in <nav and <article ?

[rognoni]

Hi all,
sorry for this newbie question: What is the best way to reduce default margin/padding in <nav and <article ?

See here my example:

[rognoni]

I am studying these:

• https://picocss.com/docs/customization.html
• https://github.com/picocss/pico/blob/master/css/themes/default.css

[rognoni]

:root {
  --spacing: 0;
}