:root {
  color-scheme: light;
  --bg: #deedf1;
  --panel: rgba(250, 252, 252, 0.84);
  --panel-strong: #f8fbfb;
  --border: rgba(57, 47, 38, 0.12);
  --text: #231a14;
  --muted: #6c5c4f;
  --accent: #3b82f6;
  --accent-strong: #2563eb;
  --accent-soft: rgba(59, 130, 246, 0.12);
  --danger: #b74848;
  --danger-soft: rgba(183, 72, 72, 0.12);
  --shadow: 0 24px 64px rgba(98, 149, 164, 0.08);
  --radius-xl: 28px;
  --radius-lg: 20px;
  --radius-md: 14px;
  --font-sans: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-serif: "Georgia", "Times New Roman", serif;
}

html,
body {
  margin: 0;
  min-height: 100%;
  background:
    radial-gradient(circle at 14% 18%, rgba(147, 216, 223, 0.5), transparent 24%),
    radial-gradient(circle at 74% 12%, rgba(197, 230, 234, 0.42), transparent 24%),
    radial-gradient(circle at 18% 72%, rgba(154, 217, 224, 0.34), transparent 30%),
    radial-gradient(circle at 86% 78%, rgba(218, 237, 240, 0.24), transparent 24%),
    var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
}

body {
  min-height: 100vh;
}

* {
  box-sizing: border-box;
}

button,
select,
textarea {
  font: inherit;
}

.hidden {
  display: none !important;
}

.chat-shell {
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  gap: 20px;
  min-height: 100vh;
  padding: 20px;
}

.chat-sidebar,
.chat-main {
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  background: var(--panel);
  backdrop-filter: blur(14px);
  box-shadow: var(--shadow);
}

.chat-sidebar {
  display: flex;
  flex-direction: column;
  gap: 18px;
  padding: 24px;
}

.brand-block h1,
.chat-header h2 {
  margin: 0;
  font-family: var(--font-serif);
  font-weight: 600;
  letter-spacing: -0.03em;
}

.brand-block h1 {
  font-size: 2rem;
}

.chat-header h2 {
  font-size: 1.85rem;
}

.eyebrow {
  margin: 0 0 8px;
  color: var(--muted);
  font-size: 0.76rem;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}

.brand-copy,
.hint-copy,
.status-meta,
.composer-hint {
  margin: 0;
  color: var(--muted);
  line-height: 1.65;
  font-size: 0.94rem;
}

.status-card,
.hint-card {
  padding: 16px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  background: var(--panel-strong);
}

.status-label,
.hint-title {
  margin: 0 0 10px;
  font-size: 0.82rem;
  color: var(--muted);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.status-value {
  margin: 0 0 6px;
  font-size: 1.1rem;
  font-weight: 700;
}

.control-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.control-group label,
.composer-label {
  font-size: 0.9rem;
  color: var(--muted);
  font-weight: 600;
}

.control-group select,
.composer textarea {
  width: 100%;
  border: 1px solid rgba(57, 47, 38, 0.15);
  border-radius: var(--radius-md);
  background: #f9fbfb;
  color: var(--text);
  outline: none;
}

.control-group select {
  min-height: 46px;
  padding: 0 14px;
}

.composer textarea {
  min-height: 120px;
  resize: vertical;
  padding: 14px 16px;
  line-height: 1.65;
}

.control-group select:focus,
.composer textarea:focus {
  border-color: rgba(31, 106, 82, 0.45);
  box-shadow: 0 0 0 4px rgba(31, 106, 82, 0.08);
}

.control-actions,
.composer-actions {
  display: flex;
  gap: 10px;
  align-items: center;
  justify-content: space-between;
}

.primary-button,
.secondary-button {
  border: 0;
  border-radius: 999px;
  padding: 12px 18px;
  cursor: pointer;
  transition:
    transform 0.18s ease,
    box-shadow 0.18s ease,
    background 0.18s ease;
}

.primary-button {
  color: #fff;
  background: linear-gradient(135deg, var(--accent), var(--accent-strong));
  box-shadow: 0 18px 34px rgba(59, 130, 246, 0.22);
}

.primary-button:hover {
  transform: translateY(-1px);
}

.secondary-button {
  color: var(--text);
  background: rgba(255, 255, 255, 0.9);
  border: 1px solid var(--border);
}

.secondary-button:hover {
  background: #fff;
}

.primary-button:disabled,
.secondary-button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
}

.chat-main {
  display: flex;
  flex-direction: column;
  min-height: 0;
}

.chat-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  padding: 24px 28px 18px;
  border-bottom: 1px solid var(--border);
}

.header-state {
  padding: 10px 14px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 0.92rem;
  font-weight: 700;
}

.error-banner {
  margin: 18px 28px 0;
  padding: 14px 16px;
  border-radius: var(--radius-md);
  background: var(--danger-soft);
  color: var(--danger);
  line-height: 1.6;
  font-size: 0.94rem;
}

.messages {
  flex: 1;
  min-height: 0;
  overflow: auto;
  padding: 24px 28px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.message {
  display: flex;
  flex-direction: column;
  gap: 8px;
  max-width: min(860px, 100%);
}

.message.user {
  align-self: flex-end;
}

.message.assistant {
  align-self: flex-start;
}

.message-role {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--muted);
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.message-body {
  padding: 15px 18px;
  border-radius: 18px;
  background: #f9fbfb;
  border: 1px solid var(--border);
  line-height: 1.7;
  white-space: pre-wrap;
  word-break: break-word;
}

.message.user .message-body {
  background: linear-gradient(135deg, var(--accent), var(--accent-strong));
  color: #fff;
  border-color: transparent;
}

.composer {
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 20px 28px 28px;
  border-top: 1px solid var(--border);
}

@media (max-width: 980px) {
  .chat-shell {
    grid-template-columns: 1fr;
  }

  .chat-sidebar {
    order: 2;
  }

  .chat-main {
    order: 1;
    min-height: 72vh;
  }
}

@media (max-width: 640px) {
  .chat-shell {
    padding: 12px;
    gap: 12px;
  }

  .chat-sidebar,
  .chat-main {
    border-radius: 22px;
  }

  .chat-header,
  .messages,
  .composer {
    padding-left: 16px;
    padding-right: 16px;
  }

  .chat-header {
    flex-direction: column;
  }

  .control-actions,
  .composer-actions {
    flex-direction: column;
    align-items: stretch;
  }
}