:root{
  --bg1:#1b2a3a;
  --bg2:#0f1720;

  --text:#ffffff;
  --muted:rgba(255,255,255,0.75);

  --card1:#2b3f55;
  --card2:#1c2a3a;

  --border:rgba(255,255,255,0.10);

  --shadow:0 8px 20px rgba(0,0,0,0.35);
  --shadow-hover:0 14px 28px rgba(0,0,0,0.45);
}

body{
  margin:0;
  font-family:"Segoe UI", Roboto, Arial, sans-serif;
  background:radial-gradient(circle at top, var(--bg1), var(--bg2));
  color:var(--text);
}

/* Top bar */
header{
  display:flex;
  justify-content:space-between;
  align-items:center;
  padding:14px 22px;
  background:linear-gradient(135deg, var(--card1), var(--card2));
  border-bottom:1px solid var(--border);
  box-shadow:var(--shadow);
}

header img{
  height:40px;
  cursor:pointer;
}

/* Back button */
header .back-button{
  display:inline-block;
  font-size:0.95rem;
  font-weight:600;
  color:var(--text);
  border:1px solid var(--border);
  border-radius:10px;
  padding:10px 14px;
  text-decoration:none;
  background:linear-gradient(135deg, var(--card1), var(--card2));
  box-shadow:var(--shadow);
  transition:transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
}

header .back-button:hover{
  transform:translateY(-2px);
  box-shadow:var(--shadow-hover);
  border-color:rgba(255,255,255,0.18);
}

/* Heading */
h1{
  text-align:center;
  padding:18px 14px 10px;
  margin:0;
  font-size:2.1rem;
  font-weight:650;
  letter-spacing:1px;
  color:var(--text);
  text-shadow:none;
}

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

.node.talking{
  border:2px solid #4f86f7;
  box-shadow:
    0 0 10px rgba(79,134,247,0.7),
    0 0 20px rgba(79,134,247,0.5),
    0 0 30px rgba(79,134,247,0.35);
  animation: nodeGlow 1.6s ease-in-out infinite alternate;
}



/* Node cards */
.node{
  width:300px;
  padding:14px;
  border-radius:14px;
  border:1px solid var(--border);
  background:linear-gradient(135deg, var(--card1), var(--card2));
  color:var(--text);
  box-shadow:var(--shadow);
  transition:transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
}

.node:hover{
  transform:translateY(-2px);
  box-shadow:var(--shadow-hover);
  border-color:rgba(255,255,255,0.18);
}

.node.talking{
  border:2px solid rgba(255,255,255,0.22);
}

/* Node text */
.node h2{
  margin:0 0 10px;
  color:var(--text);
  font-size:1.15rem;
  font-weight:650;
}

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

/* Footer */
footer{
  text-align:center;
  padding:20px;
  margin-top:20px;
  background:transparent;
  color:rgba(255,255,255,0.60);
  border-top:1px solid var(--border);
  font-size:0.85rem;
}

footer a{
  color:rgba(255,255,255,0.80);
  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;
  }
}


@keyframes nodeGlow{
  from{
    box-shadow:
      0 0 8px rgba(79,134,247,0.6),
      0 0 16px rgba(79,134,247,0.45);
  }
  to{
    box-shadow:
      0 0 14px rgba(79,134,247,0.85),
      0 0 28px rgba(79,134,247,0.65),
      0 0 40px rgba(79,134,247,0.45);
  }
}