:root {
  --bg: #0b0f19;
  --card: #151927;
  --text: #e0e0e0;
  --border: rgba(100, 100, 255, .25);
}
.light {
  --bg: #f2f2f5;
  --card: #ffffff;
  --text: #222;
  --border: rgba(80,80,160,.2);
}
body {
  margin: 0;
  padding: 20px;
  background: var(--bg);
  color: var(--text);
  font-family: 'Poppins','Noto Sans TC',sans-serif;
}
h2 {
  text-align: center;
  background: linear-gradient(90deg,#4D6BFF,#A06BFF);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}
.box {
  background: var(--card);
  padding: 20px;
  border-radius: 18px;
  border: 1px solid var(--border);
  margin-bottom: 20px;
}
input {
  width: 100%;
  padding: 14px;
  margin-top: 10px;
  background: #1a1f2e;
  color: white;
  border: none;
  border-radius: 10px;
  font-size: 17px;
}
.light input {
  background: #f7f7ff;
  color: #222;
}
button {
  width: 100%;
  padding: 15px;
  margin-top: 15px;
  background: linear-gradient(90deg,#4D6BFF,#A06BFF);
  border: none;
  border-radius: 12px;
  font-size: 20px;
  color: white;
  font-weight: bold;
}
.card {
  background: var(--card);
  padding: 15px;
  border-radius: 15px;
  border: 1px solid var(--border);
  margin-top: 10px;
}