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

:root {
  --blue-50:  #e3f2fd;
  --blue-100: #bbdefb;
  --blue-500: #2196f3;
  --blue-600: #1e88e5;
  --blue-700: #1565c0;

  --gray-50:  #fafafa;
  --gray-100: #f5f5f5;
  --gray-200: #eeeeee;
  --gray-300: #e0e0e0;
  --gray-400: #bdbdbd;
  --gray-500: #9e9e9e;
  --gray-600: #757575;
  --gray-700: #616161;
  --gray-800: #424242;
  --gray-900: #212121;

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-xl: 24px;

  --shadow-sm: 0 1px 3px rgba(0,0,0,.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,.1);

  --font: 'Segoe UI', system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
}

html, body {
  height: 100%;
  font-family: var(--font);
  background: var(--gray-100);
  color: var(--gray-900);
  -webkit-font-smoothing: antialiased;
}

.app {
  display: flex;
  flex-direction: column;
  max-width: 720px;
  height: 100dvh;
  margin: 0 auto;
  background: #fff;
  box-shadow: var(--shadow-md);
}

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 20px;
  background: #fff;
  border-bottom: 1px solid var(--gray-200);
  flex-shrink: 0;
}

.header__logo {
  display: flex;
  align-items: center;
  gap: 10px;
}

.header__logo-img {
  width: 36px;
  height: 36px;
}

.header__title {
  font-size: 17px;
  font-weight: 700;
  color: var(--blue-700);
  display: block;
  line-height: 1.2;
}

.header__subtitle {
  font-size: 12px;
  color: var(--gray-500);
  display: block;
  line-height: 1.2;
}

.header__status {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  color: var(--gray-600);
}

.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #4caf50;
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: .5; }
}

.chat {
  flex: 1;
  overflow-y: auto;
  padding: 20px 20px 10px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  scroll-behavior: smooth;
}

.chat__welcome {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  gap: 12px;
  padding: 40px 20px;
  flex: 1;
}

img.chat__welcome-icon {
  width: 64px;
  height: 64px;
  opacity: .8;
}

.chat__welcome h2 {
  font-size: 20px;
  font-weight: 700;
  color: var(--gray-800);
}

.chat__welcome p,
.chat__welcome .chat__welcome-desc {
  font-size: 14px;
  color: var(--gray-500);
  max-width: 400px;
  line-height: 1.5;
  margin: 0;
}

.chat__welcome-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 4px;
  font-size: 13.5px;
  color: var(--blue-600);
  text-decoration: none;
  transition: color .15s;
}
.chat__welcome-link:hover {
  color: var(--blue-700);
  text-decoration: underline;
}

.bubble {
  max-width: 85%;
  padding: 12px 16px;
  border-radius: var(--radius-lg);
  font-size: 14px;
  line-height: 1.6;
  word-break: break-word;
  animation: fadeUp .25s ease-out;
}

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

.bubble--user {
  align-self: flex-end;
  background: var(--blue-500);
  color: #fff;
  border-bottom-right-radius: 6px;
}

.bubble--bot {
  align-self: flex-start;
  background: var(--gray-100);
  color: var(--gray-900);
  border-bottom-left-radius: 6px;
}

.bubble--bot code {
  background: var(--gray-200);
  padding: 1px 5px;
  border-radius: 4px;
  font-size: 13px;
  font-family: 'Consolas', 'Menlo', monospace;
}

.bubble--bot pre {
  background: var(--gray-800);
  color: #e0e0e0;
  padding: 10px 14px;
  border-radius: var(--radius-sm);
  overflow-x: auto;
  margin: 8px 0;
  font-size: 12.5px;
  line-height: 1.5;
  font-family: 'Consolas', 'Menlo', monospace;
}

.bubble--bot pre code {
  background: transparent;
  padding: 0;
  color: inherit;
  font-size: inherit;
}

.bubble--bot b, .bubble--bot strong {
  font-weight: 600;
}

.bubble--bot a {
  color: var(--blue-600);
  text-decoration: underline;
  text-underline-offset: 2px;
  word-break: break-all;
}
.bubble--bot a:hover {
  color: var(--blue-700);
}

.bubble--error {
  align-self: flex-start;
  background: #fdecea;
  color: #b71c1c;
  border-bottom-left-radius: 6px;
}

.bubble--status {
  align-self: flex-start;
  background: var(--blue-50);
  color: var(--gray-700);
  border-bottom-left-radius: 6px;
  font-size: 13.5px;
}
.bubble--status b {
  font-weight: 600;
  color: var(--gray-800);
}

.typing {
  display: flex;
  gap: 5px;
  align-items: center;
  padding: 12px 18px;
  align-self: flex-start;
  background: var(--gray-100);
  border-radius: var(--radius-lg);
  border-bottom-left-radius: 6px;
}

.typing span {
  width: 7px;
  height: 7px;
  background: var(--gray-400);
  border-radius: 50%;
  animation: typingBounce .6s infinite alternate;
}
.typing span:nth-child(2) { animation-delay: .15s; }
.typing span:nth-child(3) { animation-delay: .3s; }

@keyframes typingBounce {
  from { transform: translateY(0); opacity: .4; }
  to   { transform: translateY(-4px); opacity: 1; }
}

.bubble--bot .media-grid {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  margin-top: 10px;
}
.bubble--bot .media-grid img {
  max-width: 200px;
  max-height: 180px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: transform .15s;
}
.bubble--bot .media-grid img:hover {
  transform: scale(1.03);
}

.username-bar {
  border-top: 1px solid var(--gray-200);
  background: var(--gray-50);
  flex-shrink: 0;
}

.username-toggle {
  display: flex;
  align-items: center;
  gap: 6px;
  width: 100%;
  padding: 8px 20px;
  border: none;
  background: transparent;
  cursor: pointer;
  font-size: 12.5px;
  color: var(--gray-500);
  text-align: left;
  font-family: var(--font);
  transition: color .15s;
}
.username-toggle:hover { color: var(--blue-600); }

.username-input-wrap {
  display: none;
  align-items: center;
  gap: 8px;
  padding: 0 20px 10px;
}
.username-input-wrap.open { display: flex; }

.username-at {
  font-size: 14px;
  color: var(--gray-400);
  font-weight: 600;
}

.username-input {
  flex: 1;
  border: 1px solid var(--gray-300);
  border-radius: var(--radius-sm);
  padding: 6px 10px;
  font-size: 13px;
  font-family: var(--font);
  outline: none;
  transition: border-color .15s;
}
.username-input:focus { border-color: var(--blue-500); }

.username-save {
  padding: 6px 14px;
  border: none;
  border-radius: var(--radius-sm);
  background: var(--blue-500);
  color: #fff;
  font-size: 12.5px;
  cursor: pointer;
  font-family: var(--font);
  transition: background .15s;
}
.username-save:hover { background: var(--blue-600); }

.input-area {
  padding: 12px 20px 16px;
  border-top: 1px solid var(--gray-200);
  background: #fff;
  flex-shrink: 0;
}

.input-wrap {
  display: flex;
  align-items: flex-end;
  gap: 8px;
  background: var(--gray-50);
  border: 1px solid var(--gray-300);
  border-radius: var(--radius-md);
  padding: 6px 8px 6px 14px;
  min-height: 48px;
  transition: border-color .15s;
}
.input-wrap:focus-within { border-color: var(--blue-500); }

.input-field {
  flex: 1;
  border: none;
  background: transparent;
  font-size: 14px;
  font-family: var(--font);
  resize: none;
  outline: none;
  max-height: 120px;
  line-height: 1.5;
  color: var(--gray-900);
  padding: 7px 0;
  margin: 0;
}
.input-field::placeholder {
  color: var(--gray-400);
}

.send-btn {
  width: 36px;
  height: 36px;
  border: none;
  border-radius: 50%;
  background: var(--blue-500);
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: background .15s, opacity .15s;
}
.send-btn:disabled { opacity: .4; cursor: default; }
.send-btn:not(:disabled):hover { background: var(--blue-600); }

.input-hint {
  font-size: 11.5px;
  color: var(--gray-400);
  text-align: center;
  margin-top: 8px;
}

@media (max-width: 720px) {
  .app {
    max-width: 100%;
    box-shadow: none;
  }
}

.lightbox {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,.85);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  cursor: zoom-out;
  animation: fadeIn .2s ease-out;
}
.lightbox img {
  max-width: 90vw;
  max-height: 90vh;
  border-radius: var(--radius-sm);
}
@keyframes fadeIn {
  from { opacity: 0; }
  to   { opacity: 1; }
}