body {
  margin: 0;
  font-family: "IBM Plex Sans", "Segoe UI", Arial, sans-serif;
  background:
    radial-gradient(circle at top left, rgba(53, 125, 255, 0.22), transparent 28%),
    radial-gradient(circle at top right, rgba(103, 217, 255, 0.16), transparent 22%),
    linear-gradient(180deg, #06101d 0%, #081323 52%, #091626 100%);
  color: #e2e8f0;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
}
.box {
  width: 420px;
  background: rgba(9, 18, 34, 0.9);
  border: 1px solid rgba(129, 170, 226, 0.22);
  border-radius: 24px;
  padding: 30px;
  box-shadow: 0 28px 64px rgba(2, 6, 23, 0.42);
  backdrop-filter: blur(12px);
}
input, button {
  box-sizing: border-box;
  width: 100%;
  padding: 12px 14px;
  margin-top: 10px;
  border-radius: 14px;
  border: 1px solid rgba(129, 170, 226, 0.18);
  background: rgba(9, 18, 34, 0.9);
  color: #e2e8f0;
}
input:focus, button:focus {
  outline: none;
  border-color: rgba(103, 217, 255, 0.44);
  box-shadow: 0 0 0 3px rgba(103, 217, 255, 0.12);
}
button {
  appearance: none;
  -webkit-appearance: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  cursor: pointer;
  background: linear-gradient(135deg, #357dff 0%, #67d9ff 100%);
  color: #f8fbff;
  font-weight: 700;
  font-size: 15px;
  line-height: 1;
  box-shadow: 0 18px 30px rgba(53, 125, 255, 0.22);
  transition: transform 140ms ease, box-shadow 140ms ease, filter 140ms ease;
}
button:hover {
  transform: translateY(-1px);
  box-shadow: 0 22px 36px rgba(53, 125, 255, 0.28);
  filter: saturate(1.05);
}
button:active {
  transform: translateY(0);
}
h2 {
  margin: 0 0 8px;
  text-align: center;
  font-size: 26px;
  letter-spacing: -0.03em;
}
.err { color: #fca5a5; margin-top: 12px; }