:root{
  --bg-color:#1c1b29;
  --bg-color-2:#151421;
  --text-color:#d4d4ff;
  --muted-color:#aeb3d9;
  --highlight-color:#4f86f7;
  --highlight-hover:#3a6dc9;
  --card-bg-color:#2a2738;
  --card-bg-color-2:#312d44;
  --border-color:#393552;
  --shadow:0 8px 24px rgba(0,0,0,0.28);
}

html.light-theme{
  --bg-color:#f5f6fb;
  --bg-color-2:#e8eaf3;
  --text-color:#1c1b29;
  --muted-color:#5c607a;
  --highlight-color:#4f86f7;
  --highlight-hover:#3a6dc9;
  --card-bg-color:#ffffff;
  --card-bg-color-2:#f1f2f8;
  --border-color:#d6d9e6;
  --shadow:0 8px 20px rgba(0,0,0,0.08);
}




body{
  margin:0;
  font-family:Arial, sans-serif;
  background:linear-gradient(180deg, var(--bg-color), var(--bg-color-2));
  color:var(--text-color);
}

/* Top bar */
header{
  display:flex;
  justify-content:space-between;
  align-items:center;
  padding:12px 20px;
  background:linear-gradient(180deg, var(--card-bg-color), var(--card-bg-color-2));
  border-bottom:1px solid var(--border-color);
  box-shadow:var(--shadow);
}

header img{
  height:48px;
  cursor:pointer;
}

/* Back button */
header .back-button{
  display:inline-block;
  background-color:transparent;
  color:var(--highlight-color);
  border:2px solid var(--highlight-color);
  border-radius:6px;
  padding:10px 15px;
  font-size:1em;
  font-weight:700;
  cursor:pointer;
  text-decoration:none;
  transition:background-color 0.25s ease, color 0.25s ease, transform 0.2s ease;
}

header .back-button:hover{
  background-color:var(--highlight-color);
  color:#fff;
  transform:translateY(-1px);
}

/* Heading */
h1{
  text-align:center;
  padding:18px 14px 10px;
  margin:0;
  font-size:2rem;
  font-weight:800;
  letter-spacing:1px;
  color:var(--highlight-color);
  text-shadow:0 1px 2px rgba(0,0,0,0.45);
}

/* Layout */
.container{
  max-width:1100px;
  margin:0 auto;
  padding:18px;
  display:flex;
  flex-wrap:wrap;
  gap:14px;
  justify-content:center;
}

/* Node cards */
.node{
  width:300px;
  padding:14px;
  border-radius:8px;
  border:1px solid var(--border-color);
  background:linear-gradient(180deg, var(--card-bg-color), var(--card-bg-color-2));
  color:var(--text-color);
  box-shadow:var(--shadow);
  transition:transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.node:hover{
  transform:translateY(-2px);
  box-shadow:0 10px 28px rgba(0,0,0,0.34);
  border-color:#4b4667;
}

.node.talking{
  border:2px solid var(--highlight-color);
  box-shadow:0 0 16px rgba(79,134,247,0.45);
}

/* Node text */
.node h2{
  margin:0 0 10px;
  color:var(--highlight-color);
  font-size:1.1rem;
  font-weight:700;
}

.node p{
  margin:6px 0;
  color:var(--muted-color);
}

/* Footer */
footer{
  text-align:center;
  padding:20px;
  margin-top:20px;
  background:linear-gradient(180deg, var(--card-bg-color), var(--card-bg-color-2));
  color:var(--muted-color);
  border-top:1px solid var(--border-color);
  font-size:0.9rem;
}

footer a{
  color:var(--highlight-color);
  text-decoration:none;
}

footer a:hover{
  text-decoration:underline;
}

/* Mobile */
@media (max-width:768px){
  header{
    flex-direction:column;
    gap:10px;
    text-align:center;
  }

  header .back-button{
    width:100%;
    text-align:center;
  }

  .container{
    padding:12px;
  }

  .node{
    width:100%;
  }

  h1{
    font-size:1.7rem;
  }
}

body{
  transition: background 0.25s ease, color 0.25s ease;
}

.node{
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease, background 0.25s ease;
}