:root {
  color-scheme: dark;
  --bg: #131314;
  --panel: #1e1f20;
  --panel-2: #232427;
  --border: #313234;
  --text: #e3e3e3;
  --text-dim: #9aa0a6;
  --accent: #a8c7fa;
  --accent-bg: #2b3b52;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  height: 100%;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 14px;
}

.layout {
  display: grid;
  grid-template-columns: 260px 1fr 320px;
  height: 100vh;
}

@media (max-width: 900px) {
  .layout { grid-template-columns: 1fr; grid-template-rows: auto 1fr auto; height: auto; min-height: 100vh; }
  .col.sources { max-height: 220px; overflow-y: auto; }
}

.col {
  display: flex;
  flex-direction: column;
  border-right: 1px solid var(--border);
  min-width: 0;
}
.col.studio { border-right: none; }

.col-header {
  padding: 14px 16px;
  font-weight: 600;
  border-bottom: 1px solid var(--border);
  color: var(--text-dim);
  text-transform: uppercase;
  font-size: 11px;
  letter-spacing: .06em;
}

/* Sources tree */
.tree { padding: 8px; overflow-y: auto; flex: 1; }
.tree-node { user-select: none; }
.tree-row {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 5px 8px;
  border-radius: 6px;
  cursor: pointer;
}
.tree-row:hover { background: var(--panel-2); }
.tree-row.selected { background: var(--accent-bg); color: var(--accent); }
.tree-children { margin-left: 14px; }
.tree-row .icon { opacity: .7; font-size: 12px; width: 14px; text-align: center; }

/* Chat */
.chat { background: var(--bg); }
.messages { flex: 1; overflow-y: auto; padding: 16px; display: flex; flex-direction: column; gap: 12px; }
.empty-hint { color: var(--text-dim); text-align: center; margin-top: 40px; }
.msg { max-width: 80%; padding: 10px 14px; border-radius: 12px; line-height: 1.5; white-space: pre-wrap; }
.msg.user { align-self: flex-end; background: var(--accent-bg); color: var(--accent); }
.msg.assistant { align-self: flex-start; background: var(--panel); }
.msg.error { align-self: flex-start; background: #4a2323; color: #f2b8b5; }

.chat-input {
  display: flex;
  gap: 8px;
  padding: 12px;
  border-top: 1px solid var(--border);
}
.chat-input input {
  flex: 1;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 10px 16px;
  color: var(--text);
  font-size: 14px;
}
.chat-input button {
  background: var(--accent);
  color: #052a54;
  border: none;
  border-radius: 50%;
  width: 38px;
  height: 38px;
  font-size: 16px;
  cursor: pointer;
}

/* Studio */
.studio { background: var(--bg); }
.studio-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  padding: 12px;
}
.studio-btn {
  background: var(--panel);
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: 10px;
  padding: 14px 10px;
  cursor: pointer;
  font-size: 13px;
}
.studio-btn:hover { background: var(--panel-2); }
.studio-btn.summary { grid-column: 1 / -1; }

.studio-panel {
  margin: 0 12px 12px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px;
}
.studio-panel label { display: block; font-size: 11px; color: var(--text-dim); margin: 8px 0 4px; }
.studio-panel input, .studio-panel select {
  width: 100%;
  background: var(--panel-2);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  padding: 6px 8px;
}
.studio-panel button.generate {
  margin-top: 10px;
  width: 100%;
  background: var(--accent);
  color: #052a54;
  border: none;
  border-radius: 8px;
  padding: 8px;
  cursor: pointer;
  font-weight: 600;
}

.studio-results { flex: 1; overflow-y: auto; padding: 0 12px 12px; display: flex; flex-direction: column; gap: 10px; }
.result-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px;
  font-size: 13px;
}
.flashcard {
  background: var(--panel-2);
  border-radius: 8px;
  padding: 10px;
  margin-bottom: 8px;
  cursor: pointer;
}
.flashcard .back { color: var(--text-dim); margin-top: 6px; display: none; }
.flashcard.flipped .back { display: block; }
.quiz-q { margin-bottom: 14px; }
.quiz-opt { padding: 4px 0; }
.quiz-opt.correct { color: #9adf9a; }

.error-banner {
  background: #4a2323;
  color: #f2b8b5;
  padding: 8px 12px;
  border-radius: 8px;
  font-size: 12px;
  margin: 0 12px 12px;
}