/* 배경 그라데이션 움직임 */
body {
  margin: 0;
  padding: 20px;
  height: 100vh;
  background: linear-gradient(-45deg, #0f2027, #203a43, #2c5364);
  background-size: 400% 400%;
  animation: gradientMove 20s ease infinite;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  color: white;
  overflow-x: hidden;
}

@keyframes gradientMove {
  0% {background-position:0% 50%;}
  50% {background-position:100% 50%;}
  100% {background-position:0% 50%;}
}

#result {
  width: 540px;
  margin: 0 auto 40px;
}

.row {
  display: flex;
  gap: 12px;
  justify-content: center;
  margin-bottom: 8px;
}

.box {
  width: 60px;
  height: 60px;
  background: #4caf50;
  border-radius: 8px;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 24px;
  font-weight: bold;
  user-select: none;
}

button {
  display: block;
  margin: 0 auto;
  padding: 14px 28px;
  font-size: 20px;
  border: none;
  border-radius: 12px;
  background: #4caf50;
  color: white;
  cursor: pointer;
  box-shadow: 0 0 12px #4caf50aa;
  transition: background 0.3s, box-shadow 0.3s, transform 0.3s;
  position: relative;
  overflow: hidden;
}

button:hover {
  background: #66bb6a;
  box-shadow: 0 0 20px #66bb6aee;
  transform: scale(1.05);
}

/* 별 기본 스타일 */
.star {
  position: fixed;
  top: -10px;
  width: 6px;
  height: 6px;
  background: white;
  border-radius: 50%;
  filter: drop-shadow(0 0 4px white);
  opacity: 0.8;
  animation-name: fall;
  animation-timing-function: linear;
  animation-fill-mode: forwards;
  pointer-events: none;
  z-index: 9999;
}

@keyframes fall {
  to {
    transform: translateY(110vh);
    opacity: 0;
  }
}