h1 {
display: flex;
}
h2 {
display: flex;
}
h3 {
display: flex;
}
h4 {
display: flex;
}
h5 {
display: flex;
}
h6 {
display: flex;
}

Surprisingly the original author is here, I am very happy you to reply to me, I want to ask you a question.Adding some code in preview.css can make the heading more like an outline, as shown in the figure, but the content under the heading is very prominent, such as this Hello, is there any solution?