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

:root {
  --bg: #0d0d0d;
  --text: #d4d4d4;
  --border: #222;
  --logo: #c0c0c0;
  --scrollbar: #2a2a2a;
  --bubble-assistant: #1a1a1a;
  --bubble-user: #242424;
  --bubble-user-text: #b8b8b8;
  --avatar-assistant: #3a3a3a;
  --avatar-assistant-text: #aaa;
  --avatar-user: #2a2a2a;
  --avatar-user-text: #888;
  --input-bg: #1a1a1a;
  --input-border: #2e2e2e;
  --input-border-focus: #444;
  --placeholder: #444;
  --btn-bg: #3a3a3a;
  --btn-color: #aaa;
  --btn-hover: #484848;
}

body.light {
  --bg: #f5f5f5;
  --text: #1a1a1a;
  --border: #e0e0e0;
  --logo: #333;
  --scrollbar: #ccc;
  --bubble-assistant: #fff;
  --bubble-user: #ececec;
  --bubble-user-text: #333;
  --avatar-assistant: #ddd;
  --avatar-assistant-text: #555;
  --avatar-user: #e8e8e8;
  --avatar-user-text: #777;
  --input-bg: #fff;
  --input-border: #ddd;
  --input-border-focus: #aaa;
  --placeholder: #bbb;
  --btn-bg: #ddd;
  --btn-color: #555;
  --btn-hover: #ccc;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  transition: background 0.2s, color 0.2s;
}

.chat-container {
  width: 100%;
  max-width: 720px;
  height: 100vh;
  display: flex;
  flex-direction: column;
}

.chat-header {
  padding: 32px 24px 40px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 2.2rem;
  font-weight: 600;
  letter-spacing: -0.02em;
}

.logo-gray {
  color: #888;
}

.logo-black {
  color: #111;
}

body.light .logo-black {
  color: #111;
}

body:not(.light) .logo-black {
  color: #eee;
}

#theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--logo);
  display: flex;
  align-items: center;
  padding: 4px;
  border-radius: 6px;
  transition: background 0.2s;
}

#theme-toggle:hover {
  background: var(--input-border);
}

.chat-messages {
  flex: 1;
  overflow-y: auto;
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 20px;
  scroll-behavior: smooth;
}

.chat-messages::-webkit-scrollbar {
  width: 4px;
}

.chat-messages::-webkit-scrollbar-track {
  background: transparent;
}

.chat-messages::-webkit-scrollbar-thumb {
  background: var(--scrollbar);
  border-radius: 2px;
}

.message {
  display: flex;
  gap: 12px;
  max-width: 85%;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to   { opacity: 1; transform: translateY(0); }
}

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

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

.avatar {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: var(--avatar-assistant);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  font-weight: 700;
  flex-shrink: 0;
  color: var(--avatar-assistant-text);
}

.message.user .avatar {
  background: var(--avatar-user);
  color: var(--avatar-user-text);
}

.bubble {
  background: var(--bubble-assistant);
  border-radius: 16px;
  padding: 12px 16px;
  line-height: 1.65;
  font-size: 1.06rem;
  color: var(--text);
}

.message.user .bubble {
  background: var(--bubble-user);
  color: var(--bubble-user-text);
}

.typing .bubble::after {
  content: '▋';
  animation: blink 0.8s step-start infinite;
  margin-left: 2px;
}

@keyframes blink {
  50% { opacity: 0; }
}

.chat-input-area {
  padding: 16px 24px 24px;
  border-top: 1px solid var(--border);
}

.input-wrapper {
  display: flex;
  align-items: center;
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: 12px;
  padding: 8px 8px 8px 16px;
  transition: border-color 0.2s;
}

.input-wrapper:focus-within {
  border-color: var(--input-border-focus);
}

#user-input {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  color: var(--text);
  font-size: 0.95rem;
  caret-color: var(--btn-color);
}

#user-input::placeholder {
  color: var(--placeholder);
}

#send-btn {
  width: 36px;
  height: 36px;
  border-radius: 8px;
  border: none;
  background: var(--btn-bg);
  color: var(--btn-color);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.2s, opacity 0.2s;
  flex-shrink: 0;
}

#send-btn:hover {
  background: var(--btn-hover);
}

#send-btn:disabled {
  opacity: 0.4;
  cursor: default;
}

@media (max-width: 600px) {
  .chat-messages {
    padding: 16px;
  }

  .chat-input-area {
    padding: 12px 16px 20px;
  }

  .message {
    max-width: 95%;
  }
}