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

body, html {
  height: 100%;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  color: white;
  overflow: hidden;
}

#particles-js {
  position: fixed;
  width: 100%;
  height: 100%;
  background: linear-gradient(135deg, #1e3c72, #2a5298);
  z-index: -1;
}

.container {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100%;
  padding: 20px;
}

h1 {
  margin-bottom: 20px;
  text-shadow: 2px 2px 5px rgba(0,0,0,0.3);
}

.calculator {
  background: rgba(255, 255, 255, 0.1);
  border-radius: 20px;
  padding: 20px;
  backdrop-filter: blur(10px);
  box-shadow: 0 0 15px rgba(0,0,0,0.3);
  max-width: 320px;
  width: 100%;
}

.display {
  width: 100%;
  padding: 15px;
  font-size: 24px;
  border: none;
  border-radius: 10px;
  margin-bottom: 20px;
  text-align: right;
  background: rgba(0, 0, 0, 0.2);
  color: white;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

.btn {
  padding: 20px;
  font-size: 18px;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  background-color: rgba(255, 255, 255, 0.2);
  color: white;
  transition: background-color 0.3s ease;
}

.btn:hover {
  background-color: rgba(255, 255, 255, 0.4);
}

.btn.op {
  background-color: #f39c12;
}

.btn.clear {
  background-color: #e74c3c;
}

.btn.eq {
  background-color: #2ecc71;
}

.btn.wide {
  grid-column: span 2;
}