:root {
  --bg: #ffffff;
  --bg-soft: #f7f7f8;
  --border: #e5e5e5;
  --text: #1e1e1e;
  --text-soft: #6b6b6b;
  --bubble-user: #f0f4ff;
  --bubble-assistant: #f7f7f8;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --danger: #d1373f;
  --code-bg: #f0f0f0;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #212121;
    --bg-soft: #2a2a2a;
    --border: #3a3a3a;
    --text: #ececec;
    --text-soft: #a0a0a0;
    --bubble-user: #2f3b52;
    --bubble-assistant: #2a2a2a;
    --accent: #3b82f6;
    --accent-hover: #60a5fa;
    --danger: #f87171;
    --code-bg: #1c1c1c;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
}

.app {
  display: flex;
  height: 100vh;
}

.app[hidden] {
  display: none;
}

.auth-gate {
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

.auth-gate[hidden] {
  display: none;
}

.auth-card {
  text-align: center;
  padding: 40px 36px;
  border: 1px solid var(--border);
  border-radius: 16px;
  max-width: 340px;
}

.auth-title {
  font-weight: 600;
  font-size: 18px;
  margin-bottom: 8px;
}

.auth-sub {
  color: var(--text-soft);
  font-size: 13.5px;
  margin: 0 0 20px;
}

.signin-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: var(--accent);
  color: white;
  text-decoration: none;
  padding: 10px 18px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 500;
}
.signin-btn:hover { background: var(--accent-hover); }

.user-info {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 13px;
  color: var(--text-soft);
}

.user-info a {
  color: var(--text-soft);
  text-decoration: none;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 3px 9px;
}
.user-info a:hover { color: var(--text); border-color: var(--text-soft); }

.sidebar {
  width: 260px;
  flex-shrink: 0;
  border-right: 1px solid var(--border);
  background: var(--bg-soft);
  display: flex;
  flex-direction: column;
  padding: 10px;
  overflow: hidden;
  transition: margin-left 0.15s ease;
}

.sidebar.collapsed {
  margin-left: -260px;
}

.new-chat-btn {
  background: none;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 9px 12px;
  font-size: 13.5px;
  color: var(--text);
  cursor: pointer;
  text-align: left;
  margin-bottom: 10px;
}
.new-chat-btn:hover { background: var(--bg); }

.conversation-list {
  flex: 1;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.conversation-item {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 9px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 13px;
  color: var(--text-soft);
}
.conversation-item:hover { background: var(--bg); }
.conversation-item.active {
  background: var(--bubble-user);
  color: var(--text);
}

.conversation-item .conv-title {
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.conversation-item .conv-delete {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-soft);
  font-size: 12px;
  opacity: 0;
  flex-shrink: 0;
}
.conversation-item:hover .conv-delete { opacity: 1; }

.main-col {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.topbar {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 20px;
  border-bottom: 1px solid var(--border);
}

.topbar-title {
  font-weight: 600;
  font-size: 15px;
}

.ghost-btn {
  background: none;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 6px 12px;
  font-size: 13px;
  color: var(--text);
  cursor: pointer;
}
.ghost-btn:hover { background: var(--bg-soft); }

.chat {
  flex: 1;
  overflow-y: auto;
  padding: 24px 16px 8px;
}

.msg-row {
  max-width: 760px;
  margin: 0 auto 20px;
  display: flex;
  flex-direction: column;
}

.msg-row.user { align-items: flex-end; }
.msg-row.assistant { align-items: flex-start; }

.bubble {
  max-width: 100%;
  padding: 10px 14px;
  border-radius: 14px;
  line-height: 1.55;
  font-size: 14.5px;
  white-space: normal;
  word-wrap: break-word;
}

.msg-row.user .bubble {
  background: var(--bubble-user);
  border-bottom-right-radius: 4px;
}

.msg-row.assistant .bubble {
  background: var(--bubble-assistant);
  border-bottom-left-radius: 4px;
}

.bubble p { margin: 0 0 8px; }
.bubble p:last-child { margin-bottom: 0; }
.bubble ul, .bubble ol { margin: 4px 0 8px 18px; padding: 0; }
.bubble h1, .bubble h2, .bubble h3 { margin: 10px 0 6px; }
.bubble code {
  background: var(--code-bg);
  padding: 1px 5px;
  border-radius: 4px;
  font-size: 13px;
}
.bubble pre {
  background: var(--code-bg);
  padding: 10px 12px;
  border-radius: 8px;
  overflow-x: auto;
}
.bubble pre code { background: none; padding: 0; }

.attach-chip-in-msg {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 4px 8px;
  font-size: 12.5px;
  margin: 2px 4px 2px 0;
}

.msg-img {
  max-width: 260px;
  max-height: 260px;
  border-radius: 10px;
  display: block;
  margin-bottom: 6px;
}

.bubble.streaming {
  white-space: pre-wrap;
}

.stream-text.placeholder {
  color: var(--text-soft);
  font-style: italic;
}

.stream-cursor {
  display: inline-block;
  width: 2px;
  height: 1em;
  background: var(--text-soft);
  margin-left: 2px;
  vertical-align: text-bottom;
  animation: blink 1s step-start infinite;
}

.generated-img {
  max-width: 360px;
  max-height: 360px;
  border-radius: 10px;
  display: block;
  margin: 6px 0;
}

.generated-img-row {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 4px;
}

.mermaid-block {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px;
  margin: 8px 0;
  overflow-x: auto;
  text-align: center;
}
.mermaid-block svg { max-width: 100%; height: auto; }
.mermaid-block.mermaid-error {
  color: var(--danger);
  text-align: left;
  font-size: 12.5px;
  white-space: pre-wrap;
}

.diagram-download {
  font-size: 12px;
  background: none;
  border: 1px solid var(--border);
  color: var(--text-soft);
  border-radius: 6px;
  padding: 3px 8px;
  cursor: pointer;
  margin-top: -4px;
}
.diagram-download:hover { color: var(--text); border-color: var(--text-soft); }

.auto-export-note {
  max-width: 760px;
  margin: 4px auto 0;
  font-size: 12px;
  color: var(--text-soft);
}

@keyframes blink { 0%, 50% { opacity: 1; } 50.01%, 100% { opacity: 0; } }

.error-bubble {
  color: var(--danger);
  border: 1px solid var(--danger);
  background: transparent;
}

.composer-wrap {
  border-top: 1px solid var(--border);
  padding: 10px 16px 14px;
}

.attachments {
  max-width: 760px;
  margin: 0 auto 8px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.attach-chip {
  display: flex;
  align-items: center;
  gap: 6px;
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 5px 8px;
  font-size: 12.5px;
}

.attach-chip button {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-soft);
  font-size: 13px;
  line-height: 1;
}

.composer {
  max-width: 760px;
  margin: 0 auto;
  display: flex;
  align-items: flex-end;
  gap: 8px;
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 8px 8px 8px 12px;
}

.composer textarea {
  flex: 1;
  border: none;
  background: none;
  resize: none;
  outline: none;
  font-size: 14.5px;
  font-family: inherit;
  color: var(--text);
  max-height: 200px;
  padding: 6px 0;
}

.icon-btn, .send-btn {
  border: none;
  background: none;
  cursor: pointer;
  font-size: 16px;
  width: 34px;
  height: 34px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-soft);
  flex-shrink: 0;
}
.icon-btn:hover { background: var(--border); }

.send-btn {
  background: var(--accent);
  color: white;
}
.send-btn:hover { background: var(--accent-hover); }
.send-btn:disabled { background: var(--border); color: var(--text-soft); cursor: default; }

.hint {
  max-width: 760px;
  margin: 6px auto 0;
  font-size: 11.5px;
  color: var(--text-soft);
  text-align: center;
}