/* === Cella Playground — Polished UI === */
* { margin: 0; padding: 0; box-sizing: border-box; }

:root {
  --bg-base: #1e1e2e;
  --bg-surface: #181825;
  --bg-overlay: #11111b;
  --border: #313244;
  --border-hover: #45475a;
  --text: #cdd6f4;
  --text-dim: #a6adc8;
  --text-muted: #6c7086;
  --blue: #89b4fa;
  --green: #a6e3a1;
  --red: #f38ba8;
  --yellow: #f9e2af;
  --pink: #f5c2e7;
  --mauve: #cba6f7;
  --font-mono: 'SF Mono', 'Menlo', 'Consolas', 'Liberation Mono', monospace;
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

body {
  font-family: var(--font-mono);
  background: var(--bg-base);
  color: var(--text);
  height: 100vh;
  display: flex;
  flex-direction: column;
}

/* === Header === */
header {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  padding: 0.5rem 1rem;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

header h1 { font-size: 1.1rem; color: var(--blue); font-family: var(--font-sans); }
.status { font-size: 0.8rem; color: var(--text-muted); }
.status.loaded { color: var(--green); }
.status.error { color: var(--red); }

.header-btn {
  padding: 0.25rem 0.8rem;
  font-size: 0.75rem;
  background: var(--bg-base);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text-dim);
  cursor: pointer;
  font-family: var(--font-sans);
  transition: all 0.15s;
}
.header-btn:hover { color: var(--text); border-color: var(--blue); }

/* === Route Selection === */
.route-select {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2rem;
  padding: 2rem;
}

.route-select h2 { font-size: 1.8rem; color: var(--text); font-family: var(--font-sans); }
.route-tagline { font-size: 0.95rem; color: var(--text-dim); font-style: italic; }

.route-cards { display: flex; gap: 1.5rem; flex-wrap: wrap; justify-content: center; }

.route-card {
  width: 220px;
  padding: 1.5rem;
  background: var(--bg-surface);
  border: 2px solid var(--border);
  border-radius: 12px;
  cursor: pointer;
  text-align: center;
  transition: all 0.2s;
  font-family: var(--font-sans);
}
.route-card:hover { border-color: var(--blue); transform: translateY(-3px); box-shadow: 0 8px 24px rgba(0,0,0,0.3); }
.route-card .icon { font-size: 2.5rem; margin-bottom: 0.5rem; }
.route-card .name { font-size: 1.1rem; color: var(--text); font-weight: bold; }
.route-card .subtitle { font-size: 0.8rem; color: var(--text-dim); margin-top: 0.3rem; }

.free-mode-btn {
  padding: 0.5rem 1.5rem;
  background: none;
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text-muted);
  cursor: pointer;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  transition: all 0.15s;
}
.free-mode-btn:hover { color: var(--text); border-color: var(--text); }

/* === Main Container === */
.container {
  flex: 1;
  display: flex;
  overflow: hidden;
}

/* === Collapsible === */
.collapsible > .collapse-header {
  display: flex;
  align-items: center;
  padding: 0.45rem 0.8rem;
  cursor: pointer;
  user-select: none;
  font-size: 0.8rem;
  color: var(--text-dim);
  font-weight: 600;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border);
  gap: 0.5rem;
  font-family: var(--font-sans);
  transition: background 0.15s;
}
.collapsible > .collapse-header:hover { background: var(--bg-base); color: var(--text); }
.collapse-arrow { font-size: 0.55rem; transition: transform 0.2s; color: var(--text-muted); margin-left: auto; }
.collapsible.collapsed > .collapse-header .collapse-arrow { transform: rotate(-90deg); }
.collapsible.collapsed > .collapse-body { display: none !important; }

/* === Sidebar === */
.examples-panel {
  width: 200px;
  background: var(--bg-surface);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
}

.examples-panel > .collapse-body { flex: 1; overflow-y: auto; padding: 0.4rem; }

.example-group { margin-bottom: 0.6rem; }
.example-group h3 {
  font-size: 0.65rem;
  color: var(--text-muted);
  margin-bottom: 0.2rem;
  padding: 0.2rem 0.4rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-family: var(--font-sans);
}

.example-item, .level-item {
  display: flex;
  align-items: center;
  gap: 0.3rem;
  padding: 0.35rem 0.5rem;
  font-size: 0.78rem;
  color: var(--text);
  cursor: pointer;
  border-radius: 5px;
  border: none;
  background: none;
  width: 100%;
  text-align: left;
  font-family: var(--font-sans);
  transition: background 0.1s;
  line-height: 1.3;
}
.example-item:hover, .level-item:hover { background: var(--border); }
.level-item.active { background: var(--border); color: var(--blue); }
.level-item.completed .level-status { color: var(--green); }
.level-item .level-status { font-size: 0.7rem; width: 1.2rem; text-align: center; flex-shrink: 0; }
.section-header { padding: 0.6rem 0.75rem 0.3rem; font-size: 0.7rem; font-weight: 700; text-transform: uppercase; color: var(--dim); letter-spacing: 0.05em; border-top: 1px solid var(--border); margin-top: 0.3rem; }
.section-header:first-child { border-top: none; margin-top: 0; }

/* === Editor Panel === */
.editor-panel {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.toolbar {
  display: flex;
  gap: 0.4rem;
  padding: 0.4rem 0.6rem;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
  align-items: center;
}

.toolbar button {
  padding: 0.3rem 0.9rem;
  font-size: 0.8rem;
  border: 1px solid var(--border-hover);
  border-radius: 5px;
  background: var(--border);
  color: var(--text);
  cursor: pointer;
  font-family: var(--font-sans);
  transition: all 0.1s;
}
.toolbar button:hover:not(:disabled) { background: var(--border-hover); }
.toolbar button:disabled { opacity: 0.35; cursor: not-allowed; }

#btn-check { border-color: var(--green); color: var(--green); }
#btn-run { border-color: var(--blue); color: var(--blue); }
#btn-inspect { border-color: var(--yellow); color: var(--yellow); }

.toolbar-sep { width: 1px; height: 1.2rem; background: var(--border-hover); margin: 0 0.2rem; }
.symbol-bar { display: flex; gap: 0.15rem; }
.sym-btn {
  padding: 0.15rem 0.4rem;
  font-size: 0.95rem;
  border: 1px solid var(--border-hover);
  border-radius: 4px;
  background: var(--bg-surface);
  color: var(--mauve);
  cursor: pointer;
  font-family: var(--font-mono);
  line-height: 1;
  transition: background 0.1s;
}
.sym-btn:hover { background: var(--border); }

/* === Tutorial Panel === */
.tutorial-panel {
  border-bottom: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
}

.tutorial-panel > .collapse-body {
  padding: 0.8rem 1rem;
  max-height: 40vh;
  overflow-y: auto;
  font-size: 0.85rem;
  line-height: 1.7;
  font-family: var(--font-sans);
}

.tutorial-concept {
  font-size: 0.95rem;
  font-weight: bold;
  color: var(--yellow);
  margin-bottom: 0.6rem;
  display: block;
}

.tutorial-progress { font-size: 0.75rem; color: var(--text-dim); }

.tutorial-description { color: var(--text); line-height: 1.6; }
.tutorial-description p { margin: 0.5rem 0; }
.tutorial-description p:empty { display: none; }
.tutorial-description h3 { color: var(--blue); margin: 0.8rem 0 0.3rem; font-size: 0.9rem; }
.tutorial-description h4 { color: var(--green); margin: 0.6rem 0 0.2rem; font-size: 0.85rem; }
.tutorial-description strong { color: var(--pink); }
.tutorial-description code {
  background: var(--border);
  padding: 0.1rem 0.35rem;
  border-radius: 3px;
  font-size: 0.78rem;
  color: var(--pink);
  font-family: var(--font-mono);
}

.md-codeblock {
  background: var(--bg-overlay);
  padding: 0.5rem 0.8rem;
  border-radius: 5px;
  font-size: 0.78rem;
  overflow-x: auto;
  margin: 0.5rem 0;
  border: 1px solid var(--border);
  font-family: var(--font-mono);
}

.md-table {
  border-collapse: collapse;
  margin: 0.6rem 0;
  font-size: 0.78rem;
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 6px;
  overflow: hidden;
}
.md-table th, .md-table td {
  border: 1px solid var(--border);
  padding: 0.4rem 0.6rem;
  text-align: left;
  vertical-align: top;
}
.md-table th {
  background: var(--border);
  color: var(--blue);
  font-weight: 600;
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}
.md-table td { background: var(--bg-base); }
.md-table tr:hover td { background: var(--bg-surface); }

/* === Comparison Box === */
.tutorial-comparison {
  margin-top: 0.8rem;
  border: 1px solid var(--border-hover);
  border-radius: 8px;
  overflow: hidden;
}

.comparison-title {
  background: var(--border);
  padding: 0.35rem 0.8rem;
  font-size: 0.78rem;
  color: var(--text-dim);
  font-weight: 600;
}

.comparison-body { display: flex; }

.comparison-col {
  flex: 1;
  padding: 0.6rem 0.8rem;
  font-size: 0.78rem;
  overflow-wrap: break-word;
  min-width: 0;
}
.comparison-col:first-child { border-right: 1px solid var(--border-hover); }
.comparison-col .col-label {
  font-size: 0.65rem;
  color: var(--text-muted);
  text-transform: uppercase;
  margin-bottom: 0.4rem;
  font-weight: 600;
  letter-spacing: 0.03em;
}
.comparison-col .col-content { font-size: 0.78rem; line-height: 1.6; }
.comparison-col .col-content code {
  background: var(--border);
  padding: 0.1rem 0.3rem;
  border-radius: 2px;
  font-size: 0.72rem;
  color: var(--pink);
}

.comparison-diff {
  padding: 0.4rem 0.8rem;
  font-size: 0.78rem;
  color: var(--green);
  border-top: 1px solid var(--border-hover);
  background: var(--bg-base);
  font-weight: 500;
}

.tutorial-hint {
  margin-top: 0.6rem;
  padding: 0.5rem 0.8rem;
  background: var(--bg-base);
  border-left: 3px solid var(--yellow);
  border-radius: 0 5px 5px 0;
  font-size: 0.8rem;
  color: var(--text-dim);
}

/* === Editor === */
.editor-wrapper {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-height: 0;
}
.editor-wrapper > .collapse-body { flex: 1; overflow: auto; }

/* Editor: position trick to make CodeMirror fill container */
#editor { flex: 1; position: relative; min-height: 200px; }
.cm-editor { position: absolute !important; inset: 0; }
.cm-editor .cm-scroller { overflow: auto; }

/* Mobile textarea editor */
.mobile-editor {
  width: 100%;
  min-height: 300px;
  background: var(--bg-base);
  color: var(--text);
  border: none;
  padding: 0.6rem;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  line-height: 1.5;
  resize: vertical;
  outline: none;
  tab-size: 2;
}

/* === Output === */
.output-panel {
  width: 30%;
  min-width: 200px;
  background: var(--bg-overlay);
  border-left: 1px solid var(--border);
  display: flex;
  flex-direction: column;
}
.output-panel > .collapse-body {
  flex: 1;
  padding: 0.6rem;
  overflow: auto;
  font-size: 0.82rem;
  line-height: 1.5;
  white-space: pre-wrap;
  word-break: break-word;
}

.success { color: var(--green); }
.error { color: var(--red); }
.info { color: var(--blue); }

/* === Responsive — tablet === */
@media (max-width: 1024px) {
  .output-panel { width: 28%; min-width: 180px; }
  .examples-panel { width: 170px; }
  .symbol-bar { margin-top: 0.2rem; }
}

/* === Responsive — mobile === */
@media (max-width: 768px) {
  body { height: auto; min-height: 100vh; }
  header { flex-wrap: wrap; gap: 0.4rem; padding: 0.4rem 0.6rem; }
  header h1 { font-size: 0.95rem; }
  .status { font-size: 0.7rem; }
  .header-btn { font-size: 0.65rem; padding: 0.2rem 0.5rem; }

  .route-select { padding: 1.5rem 1rem; gap: 1.2rem; }
  .route-select h2 { font-size: 1.4rem; }
  .route-tagline { font-size: 0.85rem; }
  .route-cards { flex-direction: column; align-items: stretch; gap: 0.8rem; }
  .route-card { width: 100%; padding: 1rem; }
  .route-card .icon { font-size: 2rem; }

  .container { flex-direction: column; height: auto; }

  /* Sidebar: vertical list, collapsed by default on mobile (via JS) */
  .examples-panel {
    width: 100%;
    border-right: none;
    border-bottom: 1px solid var(--border);
    flex-shrink: 0;
  }
  .examples-panel > .collapse-body {
    max-height: 35vh;
    overflow-y: auto;
    padding: 0.3rem;
  }
  .level-item, .example-item {
    font-size: 0.75rem;
    padding: 0.35rem 0.5rem;
  }

  /* Tutorial: compact */
  .tutorial-panel > .collapse-body {
    max-height: 30vh;
    font-size: 0.78rem;
    padding: 0.5rem 0.7rem;
    line-height: 1.6;
  }
  .tutorial-concept { font-size: 0.85rem; }
  .comparison-body { flex-direction: column; }
  .comparison-col:first-child { border-right: none; border-bottom: 1px solid var(--border-hover); }
  .comparison-col { padding: 0.4rem 0.6rem; font-size: 0.72rem; }

  /* Toolbar: compact */
  .toolbar { gap: 0.25rem; padding: 0.25rem 0.4rem; }
  .toolbar button { padding: 0.2rem 0.5rem; font-size: 0.7rem; border-radius: 4px; }
  .toolbar-sep { display: none; }
  .sym-btn { padding: 0.1rem 0.25rem; font-size: 0.8rem; }

  /* Editor on mobile: uses textarea, not CodeMirror */
  .editor-wrapper { flex: none !important; }
  #editor { height: auto !important; min-height: auto !important; position: static !important; }

  /* Output: bottom strip */
  .output-panel {
    width: 100%;
    min-width: auto;
    border-left: none;
    border-top: 1px solid var(--border);
    flex-shrink: 0;
  }
  .output-panel > .collapse-body {
    max-height: 25vh;
    font-size: 0.75rem;
    padding: 0.4rem;
  }

  /* Collapse headers smaller */
  .collapsible > .collapse-header { font-size: 0.72rem; padding: 0.35rem 0.5rem; }
}

/* === Very small phones === */
@media (max-width: 400px) {
  .route-card { padding: 0.8rem; }
  .route-card .icon { font-size: 1.5rem; }
  .tutorial-panel > .collapse-body { max-height: 28vh; font-size: 0.75rem; }
  #editor { min-height: 150px; }
}