body {
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
  background-color: #f9f9f9;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: start;
  height: 100vh;
  margin: 0;
  padding: 20px 10px;
}

#info {
  margin-top: 40px;
  font-size: 18px;
  color: #555;
}

#display {
  font-size: 32px;
  color: #333;
  min-height: 40px;
  text-align: center;
  margin-top: 20px;
  word-break: break-all;
}

#pad {
  display: grid;
  grid-template-columns: repeat(3, 80px);
  grid-auto-rows: 80px;
  gap: 16px;
  margin-top: 40px;
}

.btn {
  border: none;
  border-radius: 12px;
  background-color: #e0f0ff;
  color: #333;
  font-size: 24px;
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  user-select: none;
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.btn:hover {
  background-color: #cbe5ff;
}

.btn:active {
  transform: scale(0.95);
  background-color: #b3daff;
}

.btn.go {
  background: linear-gradient(135deg, #28cd41, #22a832);
  color: white;
  font-weight: bold;
  border-radius: 12px;
  box-shadow: 0 2px 6px rgba(0,0,0,0.15);
}

.btn.go:hover {
  background: linear-gradient(135deg, #20b736, #1a942a);
}

.btn.hidden {
  visibility: hidden;
}

#footer {
  margin-top: 120px;
  font-size: 12px;
  color: #888;
}