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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Microsoft YaHei", sans-serif;
  background: #f5f6fa;
  color: #1f2937;
  height: 100vh;
  overflow: hidden;
}

.app {
  display: flex;
  flex-direction: column;
  height: 100vh;
  max-width: 900px;
  margin: 0 auto;
  background: #fff;
  box-shadow: 0 0 24px rgba(0, 0, 0, 0.06);
}

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 20px;
  border-bottom: 1px solid #e5e7eb;
  background: linear-gradient(90deg, #6366f1, #8b5cf6);
  color: #fff;
}

.header h1 {
  font-size: 18px;
  font-weight: 600;
}

.provider-switch {
  display: flex;
  gap: 12px;
  font-size: 14px;
}

.provider-switch label {
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 4px;
}

.chat {
  flex: 1;
  overflow-y: auto;
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.message {
  display: flex;
}

.message.user {
  justify-content: flex-end;
}

.bubble {
  max-width: 78%;
  padding: 10px 14px;
  border-radius: 14px;
  line-height: 1.6;
  white-space: pre-wrap;
  word-wrap: break-word;
  font-size: 15px;
}

.message.user .bubble {
  background: #6366f1;
  color: #fff;
  border-bottom-right-radius: 4px;
}

.message.assistant .bubble {
  background: #f1f3f8;
  color: #1f2937;
  border-bottom-left-radius: 4px;
}

.composer {
  display: flex;
  gap: 10px;
  padding: 12px 16px;
  border-top: 1px solid #e5e7eb;
  background: #fafafa;
}

.composer textarea {
  flex: 1;
  resize: none;
  height: 48px;
  padding: 12px 14px;
  border: 1px solid #d1d5db;
  border-radius: 10px;
  font-size: 15px;
  font-family: inherit;
  outline: none;
  transition: border-color 0.2s;
}

.composer textarea:focus {
  border-color: #6366f1;
}

.composer button {
  padding: 0 22px;
  border: none;
  border-radius: 10px;
  background: #6366f1;
  color: #fff;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

.composer button:hover {
  background: #4f46e5;
}

.composer button:disabled {
  background: #a5b4fc;
  cursor: not-allowed;
}

.cursor::after {
  content: "▋";
  animation: blink 1s steps(2, start) infinite;
  margin-left: 2px;
  color: #6366f1;
}

@keyframes blink {
  to {
    visibility: hidden;
  }
}