:root {
  --bg: #060b10;
  --panel: #0b1520;
  --accent: #19c3ff;
  --text: #d9f3ff;
  --muted: #7ea4b6;
  --danger: #ff6b6b;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "JetBrains Mono", "Fira Code", monospace;
  background: radial-gradient(circle at top, #12334d 0%, var(--bg) 55%);
  color: var(--text);
  display: grid;
  place-items: center;
  padding: 24px;
}

.shell {
  width: min(880px, 100%);
  background: linear-gradient(145deg, rgba(25, 195, 255, 0.08), rgba(6, 11, 16, 0.95));
  border: 1px solid rgba(25, 195, 255, 0.35);
  border-radius: 16px;
  padding: 20px;
  box-shadow: 0 0 24px rgba(25, 195, 255, 0.2);
}

.shell-header h1 {
  margin: 0;
  font-size: 2rem;
  letter-spacing: 0.08em;
}

.shell-header p {
  margin-top: 4px;
  color: var(--muted);
}

.chat-window {
  margin-top: 16px;
  min-height: 360px;
  max-height: 50vh;
  overflow-y: auto;
  border: 1px solid rgba(25, 195, 255, 0.25);
  border-radius: 12px;
  padding: 12px;
  background: rgba(5, 10, 14, 0.75);
}

.message {
  margin: 8px 0;
  line-height: 1.5;
}

.message.user {
  color: #9ff0ff;
}

.message.assistant {
  color: #d1ffe3;
}

.message.error {
  color: var(--danger);
}

.chat-form {
  margin-top: 14px;
  display: flex;
  gap: 10px;
}

.chat-form input {
  flex: 1;
  border: 1px solid rgba(25, 195, 255, 0.4);
  border-radius: 10px;
  padding: 12px;
  background: var(--panel);
  color: var(--text);
}

.chat-form button {
  border: none;
  border-radius: 10px;
  padding: 0 18px;
  background: var(--accent);
  color: #002331;
  font-weight: 700;
  cursor: pointer;
}

@media (max-width: 768px) {
  .shell {
    padding: 14px;
  }

  .chat-window {
    min-height: 300px;
  }
}