* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

body {
  background-color: #0b0f19;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
}

.calculator {
  background-color: #0e121d;
  width: 340px;
  padding: 24px;
  border-radius: 28px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
  border: 1px solid #1a202c;
}

.display {
  width: 100%;
  height: 90px;
  background: transparent;
  color: #ffffff;
  text-align: right;
  font-size: 2.5rem;
  font-weight: 600;
  padding: 10px;
  border: none;
  outline: none;
  margin-bottom: 10px;
  word-wrap: break-word;
  word-break: break-all;
}

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

button {
  height: 60px;
  border-radius: 16px;
  border: none;
  font-size: 1.25rem;
  font-weight: 600;
  color: #e2e8f0;
  background-color: #2b3548;
  cursor: pointer;
  transition: all 0.15s ease;
  display: flex;
  justify-content: center;
  align-items: center;
}

button:active {
  transform: scale(0.95);
  opacity: 0.8;
}

.btn-op {
  background-color: #1a2b3c;
  color: #38bdf8;
}

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

.btn-equal {
  background-color: #4a80f6;
  color: #ffffff;
  box-shadow: 0 4px 12px rgba(74, 128, 246, 0.3);
}