:root {
  --gray-000: #ffffff;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-400: #9ca3af;
  --gray-700: #374151;
  --gray-900: #111827;
  --blue: #2563eb;
  --focus-ring: rgba(37, 99, 235, 0.2);

  font-family: Inter, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.35;
  color: var(--gray-900);
  background: var(--gray-100);
  color-scheme: light dark;
  font-size: 15px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--gray-100);
  color: var(--gray-900);
}

.app {
  display: grid;
  grid-template-rows: auto auto 1fr;
  gap: 1rem;
  max-width: 1000px;
  min-height: 100vh;
  margin: 0 auto;
  padding: 1.25rem;
}

.app__title {
  margin: 0;
  font-size: clamp(1.18rem, 1.5vw, 1.62rem);
  color: var(--blue);
  letter-spacing: 0.01em;
}

.app__title-link {
  color: inherit;
  text-decoration: none;
  border-bottom: 1px solid transparent;
}

.app__title-link:hover,
.app__title-link:focus-visible {
  border-bottom-color: currentColor;
}

.toolbar {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.6rem;
  background: var(--gray-000);
  border: 1px solid var(--gray-200);
  padding: 0.6rem;
}

.toolbar__field {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.toolbar select,
.toolbar button {
  border: 1px solid var(--gray-200);
  background: var(--gray-000);
  color: var(--gray-900);
  padding: 0.45rem 0.65rem;
  font: inherit;
}

.toolbar button {
  cursor: pointer;
}

.toolbar select:focus,
.toolbar button:focus,
.pane__textarea:focus {
  outline: none;
  border-color: var(--blue);
  box-shadow: 0 0 0 3px var(--focus-ring);
}

.toolbar button:hover {
  border-color: var(--blue);
}

.panes {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  min-height: 0;
}

.pane {
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
  min-height: 0;
  font-size: 0.9rem;
}

.pane__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
}

.pane__hint {
  font-size: 0.8rem;
  color: var(--blue);
  font-weight: 600;
}

.pane__textarea {
  width: 100%;
  min-height: 62vh;
  resize: vertical;
  border: 1px solid var(--gray-200);
  background: var(--gray-000);
  color: var(--gray-900);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  font-size: 0.84rem;
  line-height: 1.42;
  padding: 0.72rem;
}

.output-readonly {
  background: var(--gray-200);
}

.output-readonly.error-state {
  border-color: #dc2626;
  color: #dc2626;
}

.pane__textarea.drop-target {
  border-style: dashed;
  border-color: var(--blue);
}

.footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.6rem;
  padding-top: 0.35rem;
  color: var(--gray-700);
  font-size: 0.82rem;
}

.footer a {
  color: var(--blue);
  text-decoration: none;
  border-bottom: 1px solid transparent;
}

.footer a:hover,
.footer a:focus-visible {
  border-bottom-color: currentColor;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  border: 0;
  padding: 0;
  clip-path: inset(50%);
  overflow: hidden;
  white-space: nowrap;
}

@media (prefers-color-scheme: dark) {
  :root {
    --gray-000: #111827;
    --gray-100: #1f2937;
    --gray-200: #374151;
    --gray-400: #9ca3af;
    --gray-700: #d1d5db;
    --gray-900: #f3f4f6;
    --blue: #d1d5db;
    --focus-ring: rgba(209, 213, 219, 0.22);
  }

  .output-readonly.error-state {
    border-color: #f87171;
    color: #fca5a5;
  }
}

@media (max-width: 900px) {
  .panes {
    grid-template-columns: 1fr;
  }

  .pane__textarea {
    min-height: 40vh;
  }
}