/*
 * The playground's styling. No framework and no web fonts: the page loads a
 * WebAssembly module and three small local files, and nothing else.
 *
 * The editor is a textarea layered over a <pre>. Every metric they share is
 * declared once, in the .editor block, because a difference of half a pixel in
 * any of them shows up as highlighting that drifts away from the text as you
 * scroll down.
 */

:root {
  color-scheme: light dark;
  --bg: #ffffff;
  --panel: #f6f7f9;
  --border: #d8dce2;
  --text: #1b1f24;
  --muted: #5c6570;
  --accent: #b4472f;
  --error: #a4232a;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14171c;
    --panel: #1b1f26;
    --border: #2c333d;
    --text: #e6e9ee;
    --muted: #9aa4b2;
    --accent: #e2795c;
    --error: #f0736f;
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  padding: 1.5rem 1rem 2rem;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  line-height: 1.5;
}

header {
  max-width: 76rem;
  margin: 0 auto 1.25rem;
}

h1 {
  margin: 0;
  font-size: 1.5rem;
  letter-spacing: -0.01em;
}

.tagline {
  margin: 0.25rem 0 0;
  color: var(--muted);
}

.version {
  margin: 0.25rem 0 0;
  color: var(--muted);
  font-family: var(--mono);
  font-size: 0.8rem;
}

main {
  max-width: 76rem;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  align-items: start;
}

/* One column once two panes side by side would be too narrow to read code in. */
@media (max-width: 60rem) {
  main {
    grid-template-columns: 1fr;
  }
}

.pane {
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
  background: var(--panel);
}

.pane-head {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 0.625rem;
  border-bottom: 1px solid var(--border);
  min-height: 3rem;
  flex-wrap: wrap;
}

.pane-head label {
  color: var(--muted);
  font-size: 0.85rem;
}

.spacer {
  flex: 1;
}

button,
select {
  font: inherit;
  font-size: 0.9rem;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.3rem 0.7rem;
  cursor: pointer;
}

button:hover:not(:disabled),
select:hover:not(:disabled) {
  border-color: var(--accent);
}

button:disabled,
select:disabled {
  opacity: 0.5;
  cursor: default;
}

#run {
  border-color: var(--accent);
  color: var(--accent);
  font-weight: 600;
}

.tabs {
  display: flex;
  gap: 0.25rem;
}

.tab {
  border-color: transparent;
  background: transparent;
  color: var(--muted);
}

.tab.active {
  background: var(--bg);
  border-color: var(--border);
  color: var(--text);
  font-weight: 600;
}

/*
 * The editor stack. The textarea and the <pre> are both absolutely positioned
 * over the same box and must agree on every one of these metrics.
 */
.editor {
  position: relative;
  height: 26rem;
}

.editor > #highlight,
.editor > #source {
  position: absolute;
  inset: 0;
  margin: 0;
  padding: 0.75rem;
  border: 0;
  font-family: var(--mono);
  font-size: 0.875rem;
  line-height: 1.6;
  tab-size: 2;
  white-space: pre;
  overflow: auto;
  word-wrap: normal;
}

#highlight {
  pointer-events: none;
  color: var(--text);
  background: transparent;
}

#source {
  resize: none;
  background: transparent;
  /*
   * The text itself is drawn by the <pre> underneath. Making it transparent
   * here rather than hiding the textarea keeps the caret, the selection, and
   * every native editing behaviour intact.
   */
  color: transparent;
  caret-color: var(--accent);
}

#source::selection {
  background: color-mix(in srgb, var(--accent) 30%, transparent);
}

#source:focus {
  outline: 2px solid var(--accent);
  outline-offset: -2px;
}

#output {
  margin: 0;
  padding: 0.75rem;
  height: 26rem;
  overflow: auto;
  font-family: var(--mono);
  font-size: 0.875rem;
  line-height: 1.6;
  white-space: pre;
  background: var(--bg);
}

#output.failed {
  color: var(--error);
}

footer {
  max-width: 76rem;
  margin: 1.25rem auto 0;
  color: var(--muted);
  font-size: 0.85rem;
}

footer a {
  color: var(--muted);
}

footer span {
  margin: 0 0.4rem;
}

/* The one thing the playground cannot do, said before you try it. */
.scope {
  margin: 0 0 0.6rem;
  max-width: 46rem;
}

.scope code {
  font-family: var(--mono);
  font-size: 0.95em;
}

/*
 * Token colours. The spans these apply to come from the language's own lexer,
 * so what looks like a keyword here is what the language treats as one.
 */
#highlight .keyword {
  color: #b4472f;
  font-weight: 600;
}

#highlight .builtin {
  color: #7048a8;
}

#highlight .string {
  color: #2c7a4b;
}

#highlight .number,
#highlight .literal {
  color: #a8621b;
}

#highlight .comment {
  color: #7b8794;
  font-style: italic;
}

@media (prefers-color-scheme: dark) {
  #highlight .keyword {
    color: #e2795c;
  }

  #highlight .builtin {
    color: #c3a0f0;
  }

  #highlight .string {
    color: #7fc99a;
  }

  #highlight .number,
  #highlight .literal {
    color: #e0aa6a;
  }

  #highlight .comment {
    color: #7b8794;
  }
}