<a href="">Link</a>
<button>Button</button>
<button class="large-button">Large Button</button>

<div class="form-group">
  <label for="input">Form input</label>
  <input type="text" id="input">
</div>

<details>
  <summary>Details/Summary</summary>
  <p>Hello!</p>
</details>

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

body {
  display: grid;
  justify-items: center;
  align-content: start;
  min-height: 100vh;
  gap: 2rem;
  padding: 2rem;
  font-family: system-ui, sans-serif;
  background-color: #d3e6f5;
}

:is(a, button, input, textarea, summary) {
  --outline-size: max(2px, 0.08em);
  --outline-style: solid;
  --outline-color: currentColor;
}

:is(a, button, input, textarea, summary):focus {
  outline: var(--outline-size) var(--outline-style) var(--outline-color);
  outline-offset: var(--outline-offset, var(--outline-size));
}

:is(a, button, input, textarea, summary):focus-visible {
  outline: var(--outline-size) var(--outline-style) var(--outline-color);
  outline-offset: var(--outline-offset, var(--outline-size));
}

:is(a, button, input, textarea, summary):focus:not(:focus-visible) {
  outline: none;
}

/* Focus customizations */

.large-button {
  --outline-offset: -0.25em;
}

input {
  --outline-style: dashed;
}

summary {
  --outline-color: blue;
  --outline-offset: 0.5em;
  --outline-style: dotted;
}

@media (prefers-color-scheme: dark) {
  body {
    background-color: #222;
    color: #fff;
  }

  a {
    color: yellow;
  }

  input,
  button:not([class]) {
    --outline-color: #fff;
  }

  summary {
    --outline-color: lightskyblue;
  }
}

/* demo element styles */

button {
  padding: 0.25em 0.75em;
}

button:not([class]) {
  border-radius: 0.25em;
  border: 1px solid;
}

.large-button {
  font-size: 2.35rem;
}

.form-group {
  display: grid;
  gap: 0.5rem;
}

details p {
  margin-top: 1rem;
}