/* Default (Light Mode) */
body {
  background: linear-gradient(135deg, #e6e9f0, #eef1f5);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100vh;
  margin: 0;
  font-family: 'Segoe UI', sans-serif;
  transition: background 0.3s;
}

.toggle-container {
  display: flex;
  align-items: center;
  margin-bottom: 10px;
  gap: 10px;
}

.calculator {
  background: #ffffff;
  padding: 20px;
  border-radius: 20px;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
  width: 300px;
  transition: background 0.3s;
}

#display {
  width: 100%;
  height: 50px;
  font-size: 1.5rem;
  padding: 10px;
  margin-bottom: 15px;
  border: none;
  border-radius: 10px;
  background-color: #f0f0f0;
  text-align: right;
  box-sizing: border-box;
  transition: background 0.3s, color 0.3s;
}

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

.btn {
  padding: 20px;
  font-size: 1.2rem;
  border: none;
  border-radius: 12px;
  background-color: #f7f7f7;
  cursor: pointer;
  transition: all 0.2s ease;
}

.btn:hover {
  background-color: #dbeafe;
  transform: scale(1.05);
}

.equal {
  grid-row: span 2;
  background-color: #60a5fa;
  color: white;
}

.equal:hover {
  background-color: #3b82f6;
}

.zero {
  grid-column: span 2;
}

/* Toggle Switch */
.switch {
  position: relative;
  display: inline-block;
  width: 50px;
  height: 26px;
}

.switch input {
  opacity: 0;
  width: 0;
  height: 0;
}

.slider {
  position: absolute;
  cursor: pointer;
  background-color: #ccc;
  border-radius: 34px;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  transition: .4s;
}

.slider:before {
  position: absolute;
  content: "";
  height: 20px;
  width: 20px;
  left: 4px;
  bottom: 3px;
  background-color: white;
  border-radius: 50%;
  transition: .4s;
}

input:checked + .slider {
  background-color: #4b5563;
}

input:checked + .slider:before {
  transform: translateX(24px);
}

/* 🌙 Dark Mode Styling */
body.dark {
  background: linear-gradient(135deg, #1f2937, #111827);
  color: #f9fafb;
}

body.dark .calculator {
  background: #1e293b;
}

body.dark #display {
  background-color: #334155;
  color: white;
}

body.dark .btn {
  background-color: #475569;
  color: #f9fafb;
}

body.dark .btn:hover {
  background-color: #64748b;
}

body.dark .equal {
  background-color: #3b82f6;
  color: white;
}

body.dark .equal:hover {
  background-color: #2563eb;
}