*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
html, body {
  height: 100%;
}
body {
  background-color: #000;
  color: #fff;
  font-family: 'Segoe UI', system-ui, sans-serif;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}
header {
  position: fixed;
  top: 1.5rem;
  left: 2rem;
}
.back {
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.15em;
  color: #444;
  text-decoration: none;
  transition: color 0.2s;
}
.back:hover {
  color: #fff;
}
main {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2.5rem;
}
h1 {
  font-size: clamp(2.5rem, 8vw, 6rem);
  font-weight: 900;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: #fff;
}
.btn {
  display: inline-block;
  padding: 0.75rem 2.5rem;
  border: 1px solid #fff;
  color: #fff;
  text-decoration: none;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  font-size: 0.85rem;
  font-weight: 600;
  transition: background-color 0.2s, color 0.2s;
}
.btn:hover {
  background-color: #fff;
  color: #000;
}
footer {
  padding: 1.5rem;
  font-size: 0.7rem;
  color: #444;
  letter-spacing: 0.1em;
}