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

body{
  background-color: #121212;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}
.floating-symbols {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 0; 
  overflow: hidden;
}

.floating-symbols span {
  position: absolute;
  font-size: 20px;
  color: #00fff7;
  animation: floatAnim linear infinite;
  z-index: calc(1 + var(--depth, 1));
  user-select: none;
}

.floating-symbols span:first-child,
.floating-symbols span:nth-child(2),
.floating-symbols span:nth-child(3) {
  display: none;
}


@keyframes floatAnim {
  0% {
    transform: translateY(100vh) translateX(0) scale(1);
    opacity: 0.3;
  }
  100% {
    transform: translateY(-120vh) translateX(20px) scale(1.5);
    opacity: 0;
  }
}

.calculator{
  background: #1e1e1e;
  padding: 25px;
  border-radius: 20px;
  box-sizing: 0 0 25px rgba(0 , 255 ,255 , 0.3);
  width: 320px;
  display: flex;
  flex-direction: column;
  gap: 15px;
}

#display{
  height: 60px;
  width: 100%;
  font-size: 2rem;
  text-align: right;
  padding: 10px 15px;
  border: none;
  border-radius: 10px;
  background-color: #000000;
  color: #00fff7;
  box-shadow: inset 0 0 10px rgba(0 , 255 ,255 , 0.2);

}

.buttons{
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

button{
  padding: 20px;
  font-size: 1.2rem;
  border: none;
  border-radius: 12px;
  background: #292929;
  color: #ffffff;
  cursor: pointer;
  transition: all 0.2 ease-in-out;
}
button:hover{
  background: #00fff7;
  color:#000000 ;
  transform: scale(1.05);
}

.equal{
  grid-column: span 2;
  background: #00fff7;
  color: #000;
  font-weight: bold;
}

.equal:hover{
  background: #00e6d2;
}