:root {
  --bg-main: #eaf1fc;
  /* very light blue background */
  --bg-card: #ffffff;
  /* white card background */
  --accent: #4a90e2;
  /* medium blue primary accent */
  --accent-soft: #8ab6f3;
  /* light blue soft accent */
  --accent-warm: #cce0ff;
  /* pale sky blue warm accent */
  --text-main: #1a1f3d;
  /* dark navy text */
  --text-muted: #5a637d;
  /* greyish blue muted text */
  --border: #d1d9eb;
  /* light bluish border */
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Poppins', sans-serif;
  background: linear-gradient(135deg, #eaf1fc 0%, #d6e5fb 50%, #cce0ff 100%);
  /* full radiant light blue */
  color: var(--text-main);
  line-height: 1.9;
  font-size: 18px;
  transition: background 0.5s ease;
}

header {
  padding: 5rem 1.5rem 4rem;
  text-align: center;
  background: var(--bg-main);
  border-bottom: 1px solid var(--border);
}

/* ================= HEADER TITLE ================= */
header h1 {
  font-size: 6rem;
  font-weight: 900;
  letter-spacing: 3px;
  display: inline-block;
  padding: 0.8rem 1.5rem;
  border-radius: 10px;

  /* Gradient base */
  background: linear-gradient(45deg, var(--accent) 0%, var(--accent-soft) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;

  text-shadow: 2px 2px 5px rgba(0, 0, 0, 0.1), 1px 1px 2px rgba(0, 0, 0, 0.05);
  transition: transform 0.3s ease, text-shadow 0.3s ease;
}

header h1:hover {
  transform: scale(1.05);
  text-shadow: 3px 3px 8px rgba(0, 0, 0, 0.15);
}

header .title-game {
  display: inline;
  background: linear-gradient(45deg, #4a90e2 0%, #8ab6f3 60%);
  /* medium → light blue */
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

header .title-hub {
  display: inline;
  background: linear-gradient(45deg, #8ab6f3 0%, #cce0ff 100%);
  /* light → pale blue */
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

header p {
  margin-top: 1.5rem;
  font-size: 1.25rem;
  color: var(--text-muted);
}

main {
  max-width: 1100px;
  margin: auto;
  padding: 3.5rem 1.5rem;
  display: grid;
  gap: 3rem;
}

section {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 2.5rem 2.5rem;
}

h2 {
  font-size: 2rem;
  margin-bottom: 1.2rem;
  color: var(--accent);
}

h3 {
  font-size: 1.5rem;
  margin-bottom: 0.6rem;
  color: var(--accent-soft);
}

.tree-diagram {
  margin-top: 2.5rem;
  text-align: center;
}

.tree-parent {
  margin-bottom: 2.5rem;
}

.tree-children {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.8rem;
  position: relative;
}

.tree-children::before {
  content: "";
  position: absolute;
  top: -22px;
  left: 50%;
  width: 70%;
  height: 2px;
  background: var(--accent);
  transform: translateX(-50%);
}

.node-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1.6rem 1.8rem;
}

/* ================= GAMEHUB PARENT NODE ================= */
.parent {
  display: inline-block;
  padding: 1.8rem 2.2rem;

  background: radial-gradient(circle at top left, var(--accent) 0%, var(--accent-soft) 50%, var(--accent-warm) 100%);

  border: 2px solid var(--accent);
  color: var(--text-main);
  /* dark navy text for contrast */
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
  border-radius: 14px;
  transition: transform 0.25s ease, box-shadow 0.25s ease;
}

.parent:hover {
  transform: translateY(-3px);
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.12);
}

.parent h3 {
  color: var(--text-main);
  /* ensure title stands out */
}

.child {
  position: relative;
}

.child::before {
  content: "";
  position: absolute;
  top: -22px;
  left: 50%;
  width: 2px;
  height: 22px;
  background: var(--accent);
  transform: translateX(-50%);
}

ul {
  margin-left: 1.5rem;
  margin-top: 0.6rem;
}

li {
  margin-bottom: 0.45rem;
}

.screenshots {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
  margin-top: 1.5rem;
}

.screenshots img {
  width: 100%;
  border-radius: 14px;
  border: 1px solid var(--border);
}

footer {
  margin-top: 4.5rem;
  padding: 2.5rem 1rem;
  text-align: center;
  color: var(--text-muted);
  border-top: 1px solid var(--border);
  background: var(--bg-main);
}

footer span {
  color: var(--accent);
  font-weight: 600;
}

@media (max-width: 600px) {
  header h1 {
    font-size: 4.5rem;
  }

  .tree-children::before {
    display: none;
  }
}