* {
  box-sizing: border-box;
  font-family: 'Segoe UI', sans-serif;
}

body {
  margin: 0;
  height: 100vh;
  background: radial-gradient(circle at top, #0b1222, #000);
  display: flex;
  justify-content: center;
  align-items: center;
  color: #00ffc6;
}

.container {
  text-align: center;
  max-width: 360px;
  width: 100%;
  padding: 20px;
}

.title {
  font-size: 28px;
  margin-bottom: 6px;
  text-shadow: 0 0 15px #a855ff;
}

.subtitle {
  font-size: 14px;
  opacity: 0.8;
  margin-bottom: 16px;
}

input {
  width: 100%;
  padding: 12px;
  border-radius: 10px;
  border: none;
  outline: none;
  background: #0f172a;
  color: #00ffc6;
  box-shadow: 0 0 12px rgba(0,255,198,0.3);
  margin-bottom: 20px;
}

.ball {
  width: 220px;
  height: 220px;
  margin: 0 auto 20px;
  border-radius: 50%;
  background: radial-gradient(circle at top, #1f2937, #000);
  box-shadow:
    0 0 30px rgba(168,85,255,0.6),
    inset 0 0 30px rgba(0,255,198,0.2);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: transform 0.2s;
}

.ball.thinking {
  animation: shake 0.8s infinite;
}

.ball span {
  padding: 20px;
  font-size: 16px;
  color: #fff;
  text-shadow: 0 0 10px #00ffc6;
}

button {
  padding: 12px 24px;
  border: none;
  border-radius: 12px;
  background: linear-gradient(135deg, #00ffc6, #a855ff);
  color: #000;
  font-weight: 700;
  cursor: pointer;
  box-shadow: 0 0 20px rgba(0,255,198,0.5);
}

button:hover {
  transform: scale(1.05);
}

@keyframes shake {
  0% { transform: rotate(0); }
  25% { transform: rotate(2deg); }
  50% { transform: rotate(-2deg); }
  75% { transform: rotate(2deg); }
  100% { transform: rotate(0); }
}

.back-btn {
    position: fixed;
    top: 25px;
    right: 25px;
    width: 46px;
    height: 46px;
    border-radius: 50%;
    background: rgba(0, 255, 200, 0.15);
    border: 1px solid rgba(0, 255, 200, 0.6);
    display: flex;
    align-items: center;
    justify-content: center;
    backdrop-filter: blur(6px);
    box-shadow: 0 0 18px rgba(0,255,200,.7);
    transition: 0.25s ease;
    z-index: 999;
}

.back-btn:hover {
    transform: scale(1.15);
    box-shadow: 0 0 35px rgba(0,255,200,1);
}