* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: #f6f7fb;
  color: #111827;
}

.app {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 32px;
  background: #ffffff;
  border-bottom: 1px solid #e5e7eb;
}

.logo {
  font-size: 24px;
  font-weight: 700;
}

.tag {
  font-size: 14px;
  color: #6b7280;
}

.main {
  width: 100%;
  max-width: 960px;
  margin: 0 auto;
  padding: 48px 20px;
}

.hero {
  text-align: center;
  margin-bottom: 28px;
}

.hero h1 {
  margin: 0 0 12px;
  font-size: 44px;
}

.hero p {
  margin: 0;
  font-size: 18px;
  color: #6b7280;
}

.chat-card {
  background: #fff;
  border-radius: 20px;
  padding: 20px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.06);
}

.chat-window {
  min-height: 420px;
  max-height: 420px;
  overflow-y: auto;
  padding: 10px;
  background: #f9fafb;
  border-radius: 16px;
  border: 1px solid #e5e7eb;
}

.msg {
  max-width: 75%;
  padding: 12px 14px;
  margin: 10px 0;
  border-radius: 14px;
  line-height: 1.5;
}

.msg.ai {
  background: #e8f0ff;
  color: #1f2937;
}

.msg.user {
  background: #111827;
  color: white;
  margin-left: auto;
}

.input-bar {
  display: flex;
  gap: 12px;
  margin-top: 16px;
}

.input-bar input {
  flex: 1;
  height: 48px;
  border: 1px solid #d1d5db;
  border-radius: 14px;
  padding: 0 14px;
  font-size: 16px;
}

.input-bar button {
  height: 48px;
  padding: 0 20px;
  border: none;
  border-radius: 14px;
  background: #2563eb;
  color: #fff;
  font-size: 16px;
  cursor: pointer;
}

.input-bar button:hover {
  opacity: 0.92;
}