<div class="container">
  <h1>text-indent: <span id="val">100</span>% (<strong>300px</strong>) </h1>
</div>

<div class="actions">
  <label for="percentage">text-indent:</label>
  <input type="range" id="percentage" name="percentage" min="-200" max="200" value="100" step="5">
  <span>%</span>
</div>

@import url("https://fonts.googleapis.com/css?family=Gochi+Hand");

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  width: 100vw;
  min-height: 100vh;
  margin: 0;
  background-color: #291642;
  font-family: "Gochi Hand", sans-serif;
  font-size: 100%;
  line-height: 150%;
  letter-spacing: 0.1rem;
  color: #fff;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background-blend-mode: hue;
}

.container {
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  margin-top: auto;
}

.actions {
  padding: 3vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background-color: rgba(0, 0, 0, 0.5);
  width: 100%;
  font-size: 2rem;
  margin-top: auto;
}

:root {
  --text-indent: 100%;
}

h1 {
  text-indent: var(--text-indent);
  border: 1px dotted #0ff;
  inline-size: 300px;
  block-size: 200px;
  border-radius: 5px;
  position: relative;
  white-space: nowrap;
  padding-block-start: 30%;
}

h1::before {
  content: "inline-size: 300px; block-size: 200px";
  position: absolute;
  left: 0;
  bottom: 100%;
  color: #fff;
  z-index: 2;
  font-size: 16px;
  line-height: 1.5;
  text-indent: 0;
}

label {
  margin: 0 10px;
}

const rangeElement = document.getElementById("percentage");
const spanElement = document.getElementById("val");
const strongElement = document.querySelector("strong");

rangeElement.addEventListener("change", (etv) => {
  document.documentElement.style.setProperty(
    "--text-indent",
    `${etv.target.value}%`
  );

  spanElement.textContent = etv.target.value;

  const strongElementVal = (etv.target.value * 300) / 100;

  strongElement.textContent = `${strongElementVal}px`;
});