style.css

* {
  box-sizing: inherit;
  margin: 0;
  padding: 0;
  background: none;
  border: none;
  font: inherit;
  color: inherit;
  line-height: inherit;
  text-decoration: inherit;
}

:root {
  --font-family-sans-serif: system-ui, -apple-system, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, "Noto Sans", "Liberation Sans", sans-serif,
    "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
  --font-family-monospace: Menlo, Consolas, Monaco, Liberation Mono,
    Lucida Console, monospace;

  --font-weight-semibold: 500;

  --z-index-above-codemirror: 10; /* codemirror elements have elevated z-index */

  --top-bg: #0f172a;
  --top-color: #e2e8f0;
  --top-bright: #f8fafc;

  --label-bg: #475569;
  --label-color: #f1f5f9;

  --placeholder-color: #cbd5e1;

  --overlay-bg: rgba(51, 65, 85, 0.8);
  --overlay-color: #e2e8f0;
  --overlay-dim: #cbd5e1;

  --start-bg: #6366f1;
  --start-shadow: #a5b4fc;
  --start-color: #eef2ff;

  --error-bg: #ef4444;
  --error-color: #fef2f2;
  --error-border: #ef4444;

  --warning-bg: #ca8a04;
  --warning-color: #fefce8;
  --warning-border: #ca8a04;

  --content-bg: #1e293b;
  --content-color: #e2e8f0;

  --pre-bg: #0f172a;
  --pre-color: #f1f5f9;

  --hr-color: #1e293b;

  --ad-color: #94a3b8;
}

body {
  font-family: var(--font-family-sans-serif);
  font-size: 12px;
  line-height: 1.1;
}

.app {
  flex-direction: column;
}

.app--playground {
  position: fixed;
  left: 0;
  top: 0;
  right: 0;
  bottom: 0;
  display: flex;
}

.top {
  min-height: 32px;
  background-color: var(--top-bg);
  color: var(--top-color);
  display: flex;
  align-items: center;
  padding: 0 16px;
}

.top__link {
  margin-left: 24px;
}

.top__link:hover {
  color: var(--top-bright);
}

.logo {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 1px;
  font-weight: var(--font-weight-semibold);
}

.content {
  position: relative;
  flex: 1;
  display: flex;
  overflow-y: scroll;
  background-color: var(--content-bg);
  color: var(--content-color);
}

.content--page {
  padding: 16px 32px;
  flex: none;
  flex-direction: column;
  overflow: auto;
}

.content--page > * {
  margin: 8px 0;
}

.content--page h2 {
  font-size: 24px;
  font-weight: var(--font-weight-semibold);
  margin-top: 24px;
}

.content--page pre {
  font-family: var(--font-family-monospace);
  line-height: 1.6;
  background-color: var(--pre-bg);
  color: var(--pre-color);
  padding: 8px 12px;
  overflow-x: auto;
}

.content--page p a {
  text-decoration: underline;
}

.content--page hr {
  border-top: 1px solid var(--hr-color);
  margin: 16px 0;
}

.ad {
  color: var(--ad-color);
  font-size: 12px;
  margin: 16px 0;
}

.column {
  width: 33.33%;
  height: 100%;
  display: flex;
  flex-direction: column;
}

.column:not(:first-of-type) {
  border-left: 1px solid var(--label-bg);
}

.label {
  background-color: var(--label-bg);
  color: var(--label-color);
  padding: 8px 16px;
  font-weight: var(--font-weight-semibold);
}

.textarea,
.CodeMirror {
  flex: 1;
  padding: 8px;
  font-size: 13px;
  line-height: 1.4;
}

.CodeMirror.CodeMirror {
  background-color: var(--pre-bg);
  font-family: var(--font-family-monospace);
  font-size: 12px;
}

.CodeMirror-vscrollbar::-webkit-scrollbar,
.CodeMirror-hscrollbar::-webkit-scrollbar {
  background-color: transparent;
}

.CodeMirror-placeholder.CodeMirror-placeholder.CodeMirror-placeholder {
  color: var(--placeholder-color);
}

.overlay {
  position: absolute;
  left: 0;
  top: 0;
  right: 0;
  bottom: 0;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  background-color: var(--overlay-bg);
  color: var(--overlay-color);
  z-index: var(--z-index-above-codemirror);
}

.overlay p {
  max-width: 400px;
  margin: 8px 0;
  padding: 0 8px;
  text-align: center;
}

.overlay p strong {
  font-weight: var(--font-weight-semibold);
}

.overlay p a {
  text-decoration: underline;
}

.overlay__dim {
  color: var(--overlay-dim);
}

.start {
  padding: 8px 16px;
  font-size: 14px;
  background-color: var(--start-bg);
  color: var(--start-color);
  border-bottom: 2px solid var(--start-shadow);
  cursor: pointer;
}

.start:disabled {
  opacity: 0.5;
}

.floating-error {
  position: absolute;
  left: 16px;
  right: 16px;
  bottom: 16px;
  padding: 16px;
  background-color: var(--error-bg);
  color: var(--error-color);
  border-left: 2px solid var(--error-border);
  z-index: var(--z-index-above-codemirror);
}

.floating-warning {
  position: absolute;
  left: 16px;
  right: 16px;
  bottom: 16px;
  padding: 16px;
  background-color: var(--warning-bg);
  color: var(--warning-color);
  border-left: 2px solid var(--warning-border);
  z-index: var(--z-index-above-codemirror);
}

.marker-error.marker-error {
  background-color: var(--error-bg);
  color: var(--error-color);
  box-shadow: 0 2px 0 0 var(--error-border);
}

@media all and (max-width: 799px) {
  .content {
    flex-direction: column;
  }

  .column.column {
    width: 100%;
    border-left: none;
  }

  .textarea,
  .CodeMirror {
    max-height: 300px;
  }

  .hide-on-mobile {
    display: none;
  }
}