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

:root {
  --bg:           #f6f5f1;
  --surface:      #ffffff;
  --sidebar-bg:   #eeecea;
  --border:       #e2dfd9;
  --text:         #1c1b18;
  --text-muted:   #8c897f;
  --text-sidebar: #4e4c47;
  --accent:       #5b6af0;
  --accent-hov:   #4655e8;
  --accent-soft:  #eef0fe;
  --user-bg:      #5b6af0;
  --user-text:    #ffffff;
  --bot-bg:       #ffffff;
  --active-chat:  #e0ddd6;
  --radius:       14px;
  --radius-sm:    9px;
  --sidebar-w:    252px;
  --font:         "Segoe UI", -apple-system, system-ui, sans-serif;
}

html, body { height: 100%; overflow: hidden; }

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
}

/* ── Layout ────────────────────────────────────────────── */
#app { display: flex; height: 100dvh; }

/* ── Sidebar ─────────────────────────────────────────────*/
#sidebar {
  width: var(--sidebar-w);
  min-width: var(--sidebar-w);
  background: var(--sidebar-bg);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  overflow: visible;
  transition: width 0.22s ease, min-width 0.22s ease;
  position: relative;
}

.sidebar-header, #chat-list { overflow: hidden; }

#sidebar.collapsed { width: 0; min-width: 0; }

.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 12px 10px;
  flex-shrink: 0;
}

.sidebar-brand {
  display: flex;
  align-items: center;
  gap: 8px;
}

.sidebar-logo { height: 24px; width: auto; object-fit: contain; }

.sidebar-name {
  font-size: 1rem;
  font-weight: 600;
  color: var(--accent);
  letter-spacing: -0.01em;
}

#new-chat-btn {
  width: 28px; height: 28px;
  border: none;
  background: transparent;
  border-radius: 7px;
  cursor: pointer;
  color: var(--text-muted);
  display: flex; align-items: center; justify-content: center;
  transition: background 0.14s, color 0.14s;
  flex-shrink: 0;
}
#new-chat-btn:hover { background: var(--active-chat); color: var(--text); }
#new-chat-btn svg { width: 16px; height: 16px; }

#chat-list {
  flex: 1;
  overflow-y: auto;
  padding: 0 6px 20px;
}

.chat-group-label {
  font-size: 0.67rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  padding: 12px 8px 3px;
}

.chat-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 7px 10px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  color: var(--text-sidebar);
  font-size: 0.845rem;
  transition: background 0.12s;
  white-space: nowrap;
  overflow: hidden;
}
.chat-item:hover { background: var(--active-chat); }
.chat-item.active { background: var(--active-chat); font-weight: 600; color: var(--text); }

.chat-item-icon { flex-shrink: 0; width: 13px; height: 13px; opacity: 0.38; }
.chat-item-title { overflow: hidden; text-overflow: ellipsis; }

/* ── Main ────────────────────────────────────────────────*/
#main { flex: 1; display: flex; flex-direction: column; min-width: 0; overflow: hidden; }

/* ── Header ──────────────────────────────────────────────*/
header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 0 18px;
  height: 54px;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: nowrap;
}

#sidebar-toggle {
  width: 32px; height: 32px;
  border: none;
  background: transparent;
  border-radius: var(--radius-sm);
  cursor: pointer;
  color: var(--text-muted);
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
  transition: background 0.14s, color 0.14s;
}
#sidebar-toggle:hover { background: var(--bg); color: var(--text); }
#sidebar-toggle svg { width: 17px; height: 17px; }

.header-right {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-left: auto;
  flex-shrink: 0;
}

/* Feedback — pill ghost button */
#feedback-btn {
  font-family: var(--font);
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-muted);
  background: transparent;
  border: 1.5px solid var(--border);
  border-radius: 20px;
  padding: 5px 14px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 5px;
  transition: color 0.15s, border-color 0.15s, background 0.15s;
  white-space: nowrap;
  letter-spacing: 0.01em;
}
#feedback-btn::before {
  content: "✦";
  font-size: 0.6rem;
  opacity: 0.6;
}
#feedback-btn:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-soft);
}

.model-select-wrap {
  display: flex;
  align-items: center;
  gap: 6px;
}

.model-select-wrap label {
  font-size: 0.76rem;
  color: var(--text-muted);
  font-weight: 500;
  white-space: nowrap;
}

#model-select {
  font-family: var(--font);
  font-size: 0.8rem;
  padding: 5px 8px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg);
  color: var(--text);
  cursor: pointer;
  outline: none;
  max-width: 200px;
  transition: border-color 0.14s;
}
#model-select:focus { border-color: var(--accent); }

/* ── Messages ────────────────────────────────────────────*/
#messages {
  flex: 1;
  overflow-y: auto;
  padding: 32px clamp(16px, 7vw, 90px) 16px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  scroll-behavior: smooth;
}

.msg { display: flex; max-width: 74%; animation: fadeUp 0.17s ease; }

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(7px); }
  to   { opacity: 1; transform: translateY(0); }
}

.msg.user { align-self: flex-end; flex-direction: row-reverse; }
.msg.bot  { align-self: flex-start; }

.bubble {
  padding: 11px 16px;
  border-radius: var(--radius);
  font-size: 0.925rem;
  line-height: 1.62;
  white-space: pre-wrap;
  word-break: break-word;
}

.msg.user .bubble {
  background: var(--user-bg);
  color: var(--user-text);
  border-bottom-right-radius: 3px;
  box-shadow: 0 2px 8px rgba(91,106,240,0.22);
}

.msg.bot .bubble {
  background: var(--bot-bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-bottom-left-radius: 3px;
  box-shadow: 0 1px 3px rgba(0,0,0,0.05);
}

.bubble.streaming::after {
  content: "▋";
  display: inline-block;
  animation: blink 0.85s step-end infinite;
  margin-left: 2px;
  opacity: 0.55;
}
@keyframes blink {
  0%, 100% { opacity: 0.55; }
  50% { opacity: 0; }
}

/* ── Footer ──────────────────────────────────────────────*/
footer {
  background: var(--surface);
  border-top: 1px solid var(--border);
  padding: 12px 18px 16px;
  flex-shrink: 0;
}

.input-wrap {
  display: flex;
  align-items: center;
  gap: 10px;
  background: var(--bg);
  border: 1.5px solid var(--border);
  border-radius: var(--radius);
  padding: 8px 10px 8px 14px;
  transition: border-color 0.15s, box-shadow 0.15s;
  max-width: 780px;
  margin: 0 auto;
}
.input-wrap:focus-within {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(91,106,240,0.09);
}

#input {
  flex: 1;
  font-family: var(--font);
  font-size: 0.925rem;
  background: transparent;
  border: none;
  outline: none;
  resize: none;
  color: var(--text);
  line-height: 1.55;
  max-height: 140px;
  overflow-y: auto;
}
#input::placeholder { color: var(--text-muted); }

#send-btn {
  flex-shrink: 0;
  width: 34px; height: 34px;
  border-radius: 9px;
  border: none;
  background: var(--accent);
  color: #fff;
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  transition: background 0.14s, transform 0.1s, opacity 0.15s;
  box-shadow: 0 2px 6px rgba(91,106,240,0.28);
}
#send-btn:hover { background: var(--accent-hov); transform: scale(1.05); }
#send-btn:active { transform: scale(0.96); }
#send-btn:disabled { opacity: 0.35; cursor: default; transform: none; box-shadow: none; }
#send-btn svg { width: 15px; height: 15px; }

.disclaimer {
  font-size: 0.69rem;
  color: var(--text-muted);
  text-align: center;
  margin-top: 9px;
  letter-spacing: 0.01em;
}

/* ── Empty state ─────────────────────────────────────────*/
.empty-state {
  margin: auto;
  text-align: center;
  pointer-events: none;
  user-select: none;
  padding-bottom: 48px;
}
.empty-state h2 {
  font-size: 1.45rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 7px;
  letter-spacing: -0.02em;
}
.empty-state p { font-size: 0.9rem; color: var(--text-muted); }

/* ── Scrollbars ──────────────────────────────────────────*/
#messages::-webkit-scrollbar,
#chat-list::-webkit-scrollbar { width: 4px; }
#messages::-webkit-scrollbar-track,
#chat-list::-webkit-scrollbar-track { background: transparent; }
#messages::-webkit-scrollbar-thumb,
#chat-list::-webkit-scrollbar-thumb { background: var(--border); border-radius: 9px; }

/* ── Mobile ──────────────────────────────────────────────*/
#sidebar-close {
  display: none;
  position: absolute;
  top: 50%;
  right: -22px;
  transform: translateY(-50%);
  width: 22px; height: 56px;
  border: 1.5px solid var(--border);
  border-left: none;
  background: var(--sidebar-bg);
  border-radius: 0 12px 12px 0;
  cursor: pointer;
  color: var(--text);
  align-items: center;
  justify-content: center;
  box-shadow: 4px 0 10px rgba(0,0,0,0.10);
  z-index: 101;
}
#sidebar-close svg { width: 16px; height: 16px; }

#sidebar-backdrop {
  display: none;
  position: fixed; inset: 0;
  background: rgba(0,0,0,0.28);
  z-index: 99;
}

@media (max-width: 600px) {
  #sidebar {
    position: fixed; left: 0; top: 0; bottom: 0;
    z-index: 100;
    box-shadow: 4px 0 20px rgba(0,0,0,0.09);
  }
  #sidebar.collapsed { width: 0; min-width: 0; box-shadow: none; }
  #sidebar:not(.collapsed) ~ #sidebar-backdrop { display: block; }
  #sidebar:not(.collapsed) #sidebar-close { display: flex; }
  header, footer { padding-left: 12px; padding-right: 12px; }
  .msg { max-width: 90%; }
  #model-select { max-width: 130px; }
}