Hallo. I tried to customize font size, type and color. I searched this website:
https://www.w3schools.com/css/css_font.asp
where I found this code:

p.serif {
    font-family: "Times New Roman", Times, serif;
}

p.sansserif {
    font-family: Arial, Helvetica, sans-serif;
}

<h1>CSS font-family</h1>
<p class="serif">This is a paragraph, shown in the Times New Roman font.</p>
<p class="sansserif">This is a paragraph, shown in the Arial font.</p>

The result is that the first two commands give:
p.serif null
p.sansserif null
And the last sentences are shown in the usual font.
What do I do wrong this time?

Where are you putting this code?

p.serif {
    font-family: "Times New Roman", Times, serif;
}

p.sansserif {
    font-family: Arial, Helvetica, sans-serif;
}

I would put it in the style.css file. See this thread for how to find style.css: https://textadventures.co.uk/forum/squiffy/topic/5990/how-can-i-make-the-squiffy-background-black

I tried this, it seems to work.

<div style="font-family: Times New Roman; font-size: 1em;"> 
Esempio 1 Times new roman 1em 
</div>

This does work, but as soon as the story progresses to a new section, it reverts to the default font.

It would be great if there was an easy way to change the default font from inside the Squiffy editor (i.e. not having to edit CSS).

guys I'm trying to change the font color but even if this "div" thing works, I can't figure out how to add the font color. I tried several things that sounded good but none worked, so is there someone who knows?

doesn't matter, I found it. I changed it in the Style file.
{
background: url("background.png");
color: white
}