:root {
  --bg: #f4f7f6;
  --ink: #14221f;
  --card: #ffffff;
  --line: #d7e3df;
  --accent: #0b7a6a;
  --muted: #5f736e;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: "Noto Sans TC", "Segoe UI", sans-serif;
  background:
    radial-gradient(1200px 500px at 10% -10%, #d9f3ec 0%, transparent 55%),
    linear-gradient(180deg, #eef5f3, var(--bg));
  color: var(--ink);
}
.app { max-width: 720px; margin: 0 auto; padding: 24px 16px 40px; }
.head { margin-bottom: 16px; }
.kicker { margin: 0; font-size: 12px; letter-spacing: .08em; text-transform: uppercase; color: var(--muted); }
h1 { margin: 6px 0; font-size: 1.8rem; }
.sub { margin: 0; color: var(--muted); }
.chat {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  min-height: 360px;
  max-height: 55vh;
  overflow: auto;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.bubble {
  max-width: 92%;
  padding: 10px 12px;
  border-radius: 12px;
  line-height: 1.5;
  white-space: pre-wrap;
}
.bubble.user { align-self: flex-end; background: #0b7a6a; color: #fff; }
.bubble.bot { align-self: flex-start; background: #eef6f4; border: 1px solid var(--line); }
.bubble.sys { align-self: center; color: var(--muted); font-size: 13px; background: transparent; }
.composer { display: flex; gap: 8px; margin-top: 12px; }
textarea {
  flex: 1;
  resize: vertical;
  min-height: 64px;
  padding: 12px;
  border-radius: 12px;
  border: 1px solid var(--line);
  font: inherit;
}
button {
  border: 0;
  border-radius: 12px;
  background: var(--accent);
  color: #fff;
  padding: 0 18px;
  font-weight: 600;
  cursor: pointer;
}
button:disabled { opacity: .6; cursor: wait; }
.hint { color: var(--muted); font-size: 13px; }
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0); border: 0;
}