:root {
  --bg: #0b1220;
  --fg: #e6eaf2;
  --muted: #98a2b3;
  --primary: #0ea5e9;
  --shadow: 0 6px 20px rgba(0, 0, 0, 0.25);
}

:root.light {
  --bg: #ffffff;
  --fg: #16181d;
  --muted: #667085;
  --primary: #0ea5e9;
  --shadow: 0 8px 20px rgba(2, 6, 23, 0.08);
}

* {
  box-sizing: border-box;
  transition: background-color 0.3s, color 0.3s;
}

html, body {
  height: 100%;
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Ubuntu, sans-serif;
  background: var(--bg);
  color: var(--fg);
  display: flex;
  align-items: center;
  justify-content: center;
}

.intro {
  position: relative;
  text-align: center;
  width: 100%;
  padding: 40px;
}

.container {
  max-width: 700px;
  margin: auto;
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 1s ease, transform 1s ease;
}

.container.visible {
  opacity: 1;
  transform: translateY(0);
}

h1 {
  font-size: clamp(28px, 5vw, 48px);
  font-weight: 700;
  margin-bottom: 12px;
}

h1 span {
  color: var(--primary);
}

.subtitle {
  font-size: 1.2rem;
  color: var(--muted);
  margin-bottom: 40px;
}

.links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 16px;
  margin-bottom: 30px;
}

.btn {
  display: inline-block;
  padding: 12px 20px;
  background: var(--primary);
  color: white;
  border-radius: 12px;
  text-decoration: none;
  box-shadow: var(--shadow);
  font-weight: 500;
}
.btn:hover {
  opacity: 0.9;
}

.divider {
  width: 100px;
  height: 2px;
  background: var(--primary);
  margin: 40px auto;
  border-radius: 1px;
}

.enter {
  font-size: 1.1rem;
  color: var(--fg);
  text-decoration: none;
  border-bottom: 2px solid var(--primary);
  padding-bottom: 3px;
}
.enter:hover {
  color: var(--primary);
}

#themeToggle {
  position: absolute;
  top: 16px;
  right: 16px;
  background: transparent;
  border: 1px solid var(--muted);
  border-radius: 8px;
  padding: 8px 10px;
  color: var(--fg);
  cursor: pointer;
  font-size: 1.1rem;
}

@media (max-width: 600px) {
  .btn {
    width: 100%;
    text-align: center;
  }
}