/* ── Reset ── */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

/* ── Design tokens ── */
:root {
  --color-bg: #0f1117;
  --color-surface: #1a1d27;
  --color-surface-2: #222534;
  --color-border: #2e3148;
  --color-text: #d4d8f0;
  --color-muted: #6b7394;
  --color-accent: #7c8cff;
  --color-accent-dim: #3d4580;
  --color-heading: #c4aaff;
  --color-strong: #eef0ff;
  --color-code-bg: #1e2133;
  --color-blockquote: #555c8a;
  --font-mono: "Cascadia Code", "Fira Code", Consolas, "Courier New", monospace;
  --font-sans: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --header-height: 52px;
  --radius: 6px;
}

/* ── Accessibility: screen-reader only ── */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ── Base ── */
html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

body {
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-sans);
  height: 100dvh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* ── Header ── */
.app-header {
  height: var(--header-height);
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0 1.5rem;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  flex-shrink: 0;
}

.app-title {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--color-accent);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  white-space: nowrap;
}

.app-subtitle {
  font-size: 0.75rem;
  color: var(--color-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.app-subtitle kbd {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  background: var(--color-surface-2);
  border: 1px solid var(--color-border);
  border-radius: 3px;
  padding: 0 0.3em;
  color: var(--color-text);
}

/* ── Layout ── */
.editor-layout {
  flex: 1;
  display: flex;
  min-height: 0;
}

.pane {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-width: 0;
  overflow: hidden;
}

.pane-divider {
  width: 1px;
  background: var(--color-border);
  flex-shrink: 0;
}

/* ── Pane titles ── */
.pane-title {
  font-size: 0.68rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--color-muted);
  padding: 0.5rem 1.25rem;
  border-bottom: 1px solid var(--color-border);
  background: var(--color-surface);
  flex-shrink: 0;
}

/* ── Editor textarea ── */
.editor-textarea {
  flex: 1;
  width: 100%;
  padding: 1.25rem 1.5rem;
  background: transparent;
  color: var(--color-text);
  font-family: var(--font-mono);
  font-size: 0.875rem;
  line-height: 1.75;
  border: none;
  outline: none;
  resize: none;
  caret-color: var(--color-accent);
  overflow-y: auto;
}

.editor-textarea::placeholder {
  color: var(--color-muted);
  opacity: 0.6;
}

.editor-textarea:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: -2px;
}

/* ── Preview ── */
.preview-content {
  flex: 1;
  padding: 1.25rem 1.5rem;
  overflow-y: auto;
  line-height: 1.75;
  font-size: 0.9375rem;
}

/* ── Preview typography ── */
.preview-content h1,
.preview-content h2,
.preview-content h3,
.preview-content h4,
.preview-content h5,
.preview-content h6 {
  color: var(--color-heading);
  line-height: 1.3;
  margin-top: 1.75rem;
  margin-bottom: 0.5rem;
}

.preview-content h1 { font-size: 1.9rem; }
.preview-content h2 { font-size: 1.45rem; border-bottom: 1px solid var(--color-border); padding-bottom: 0.3rem; }
.preview-content h3 { font-size: 1.15rem; }
.preview-content h4 { font-size: 1rem; }

.preview-content h1:first-child,
.preview-content h2:first-child,
.preview-content h3:first-child {
  margin-top: 0;
}

.preview-content p {
  margin: 0.85rem 0;
}

.preview-content strong {
  color: var(--color-strong);
  font-weight: 700;
}

.preview-content em {
  color: var(--color-accent);
  font-style: italic;
}

.preview-content a {
  color: var(--color-accent);
  text-decoration: underline;
  text-underline-offset: 3px;
}

.preview-content a:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  border-radius: 2px;
}

/* ── Code ── */
.preview-content code {
  font-family: var(--font-mono);
  font-size: 0.82em;
  background: var(--color-code-bg);
  color: #f8a8c8;
  padding: 0.15em 0.45em;
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
}

.preview-content pre {
  background: var(--color-code-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1rem 1.25rem;
  overflow-x: auto;
  margin: 1rem 0;
}

.preview-content pre code {
  background: none;
  border: none;
  padding: 0;
  font-size: 0.85rem;
  color: var(--color-text);
}

/* ── Lists ── */
.preview-content ul,
.preview-content ol {
  padding-left: 1.6rem;
  margin: 0.75rem 0;
}

.preview-content li {
  margin: 0.3rem 0;
}

.preview-content li > p {
  margin: 0;
}

/* ── Blockquote ── */
.preview-content blockquote {
  border-left: 3px solid var(--color-accent-dim);
  padding: 0.5rem 0 0.5rem 1.25rem;
  margin: 1rem 0;
  color: var(--color-blockquote);
  font-style: italic;
}

.preview-content blockquote > p {
  margin: 0;
}

/* ── HR ── */
.preview-content hr {
  border: none;
  border-top: 1px solid var(--color-border);
  margin: 1.5rem 0;
}

/* ── Table ── */
.preview-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0;
  font-size: 0.9em;
}

.preview-content th,
.preview-content td {
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--color-border);
  text-align: left;
}

.preview-content th {
  background: var(--color-surface-2);
  color: var(--color-strong);
  font-weight: 600;
}

.preview-content tr:nth-child(even) td {
  background: var(--color-surface);
}

/* ── Scrollbars (Webkit) ── */
::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}
::-webkit-scrollbar-track {
  background: transparent;
}
::-webkit-scrollbar-thumb {
  background: var(--color-border);
  border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--color-muted);
}

/* ── Responsive: stack on narrow screens ── */
@media (max-width: 640px) {
  body {
    overflow: auto;
  }

  .editor-layout {
    flex-direction: column;
    height: auto;
  }

  .pane {
    height: 50dvh;
  }

  .pane-divider {
    width: 100%;
    height: 1px;
  }
}

/* ── Preview-only mode (Ctrl+Enter) ── */
body.preview-only .preview-content {
  align-self: center;
  max-width: 72ch;
  width: 100%;
  padding: 2rem 1.5rem;
}

body.preview-only .app-subtitle {
  color: var(--color-accent);
}

/* ── High-contrast / forced-colors support ── */
@media (forced-colors: active) {
  .editor-textarea:focus-visible {
    outline: 3px solid Highlight;
  }
}