<div class="container">
  <div class="counter-reset">
    <h1 data-element="h1">Counter-increment</h1>
    <p data-element="p">Paragraph...</p>
    <aside data-element="aside">
      Aside...
      <p data-element="p">Paragraph...</p>
      <p data-element="p">Paragraph...</p>
    </aside>
    <p data-element="p">Paragraph...</p>
    <section data-element="section">
      Section...
      <p data-element="p">Paragraph...</p>
      <p data-element="p">Paragraph...</p>
    </section>
  </div>
</div>

@import url("https://fonts.googleapis.com/css2?family=Exo:wght@600&display=swap");

* {
  box-sizing: border-box;
}

body {
  inline-size: 100vw;
  min-block-size: 100vh;
  margin: 0;
  padding: 0;
  display: flex;
  justify-content: center;
  /*   align-items: center; */
  gap: 10px;
  font-family: "Exo", Arial, sans-serif;
  background-color: #f7f7f7;
  line-height: 2;
  padding: 20px;
}

.container {
  padding: 10px 20px;
  background: #fff;
  box-sizing: border-box;
  box-shadow: 0 2px 4px rgb(0 0 0 / 20%);
  min-width: 50vw;
  border-radius: 5px;
  position: relative;
  width: 80%;
  max-width: 60vw;
  flex: 1;
}

.counter-reset > * {
  margin: 10px 0;
}

section,
aside {
  border-right: 5px solid;
}

section > p,
aside > p {
  margin-left: 3em;
}

.counter-reset *::before {
  display: inline-flex;
  color: #fff;
  background-color: #f36;
  padding: 10px;
  line-height: 1;
  font-size: 2rem;
  margin-right: 20px;
  aspect-ratio: 1 / 1;
  justify-content: center;
  align-items: center;
  clip-path: polygon(
    0% 0%,
    89% 0,
    89% 40%,
    100% 50%,
    89% 61%,
    88% 100%,
    0 100%
  );
  border-radius: 50%;
}

section p::before {
  background: #09f !important;
  font-size: 100% !important;
}
aside p::before {
  background: #98f !important;
  font-size: 100% !important;
}

.counter-reset *::after {
  content: "(" attr(data-element) "  Element)";
  font-size: 85%;
  line-height: 1;
  color: #5c2;
  margin-left: 5px;
}

.form {
  background: rgb(0 0 0 / 0.8);
  color: #fff;
  padding: 50px 10px 10px;
  display: flex;
  flex-direction: column;
  justify-content: flex-start;
  gap: 10px;
  text-shadow: 1px 1px 0 rgb(255 125 125 / 0.8);
}

label {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  cursor: pointer;
}

.counter-reset {
  counter-reset: level1 level2-1 level2-2;
}

.counter-reset > :not(h1) {
  counter-increment: level1;
}

section p {
  counter-increment: level2-1;
}

aside p {
  counter-increment: level2-2;
}

.counter-reset > :not(h1)::before {
  content: counter(level1);
}

section p::before {
  content: counter(level1) "." counter(level2-1);
}

aside p::before {
  content: counter(level1) "." counter(level2-2);
}