body {
    font-family: Arial, sans-serif;
    margin: 0;
    height: 100vh;
    background: url('pieklo.png') no-repeat center center fixed;
    background-size: cover;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
    position: relative;
  }
  
  .calculator {
    background-color: rgba(0, 0, 0, 0.85);
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 0 30px 10px rgba(255, 0, 0, 0.5);
    width: 300px;
    z-index: 2;
  }
  
  #display {
    width: 100%;
    height: 60px;
    font-size: 2em;
    text-align: right;
    margin-bottom: 15px;
    padding: 10px;
    box-sizing: border-box;
    border: 2px solid #ff3c00;
    border-radius: 10px;
    background-color: #1a0000;
    color: #fff;
  }
  
  .buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
  }
  
  button {
    padding: 20px;
    font-size: 1.2em;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    background-color: #330000;
    color: #fff;
    transition: all 0.2s ease;
    box-shadow: 0 0 10px #ff4500;
    position: relative;
  }
  
  button:hover {
    background-color: #660000;
  }
  
  button:active::after {
    content: '';
    position: absolute;
    top: -10px;
    left: -10px;
    right: -10px;
    bottom: -10px;
    background: radial-gradient(circle, rgba(255,140,0,0.5) 0%, rgba(255,0,0,0.3) 70%);
    border-radius: 50%;
    animation: flamePulse 0.3s;
    z-index: -1;
  }
  
  @keyframes flamePulse {
    from {
      transform: scale(0.5);
      opacity: 0.8;
    }
    to {
      transform: scale(1.5);
      opacity: 0;
    }
  }
  
  button.zero {
    grid-column: span 2;
  }

  #display.fire-effect {
    animation: burnEffect 0.7s ease forwards;
  }
  
  @keyframes burnEffect {
    0% {
      box-shadow: 0 0 0px #ff6600;
      background-color: #1a0000;
    }
    50% {
      box-shadow: 0 0 30px #ff6600;
      background-color: #330000;
    }
    100% {
      box-shadow: 0 0 0px #ff6600;
      background-color: #1a0000;
    }
  }

  .spark {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 5px;
    height: 5px;
    background-color: rgba(255, 140, 0, 0.8);
    border-radius: 50%;
    animation: sparkAnimation 1.5s infinite;
    pointer-events: none;
    z-index: 1;
  }
  
  .spark:nth-child(odd) {
    animation-duration: 2s;
  }
  
  .spark:nth-child(even) {
    animation-duration: 2.5s;
  }
  
  @keyframes sparkAnimation {
    0% {
      transform: translateY(0) scale(1);
      opacity: 1;
    }
    100% {
      transform: translateY(-200px) scale(0.4);
      opacity: 0;
    }
  }  