:root {
  /* Dracula Light Theme */
  --bg-color: #f8f8f2;
  --display-bg: #e0e0e0;
  --btn-bg: #fafafa;
  --btn-color: #282a36;
  --accent-color: #bd93f9;
  --equal-bg: #ff79c6;
  --equal-color: #fff;
  --font-color: #282a36;
}

[data-theme="dark"] {
  /* Dracula Dark Theme */
  --bg-color: #282a36;
  --display-bg: #44475a;
  --btn-bg: #6272a4;
  --btn-color: #f8f8f2;
  --accent-color: #bd93f9;
  --equal-bg: #ff79c6;
  --equal-color: #fff;
  --font-color: #f8f8f2;
}

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

body {
  position: relative;
  font-family: 'Fira Code', monospace;
  background-color: var(--bg-color);
  color: var(--font-color);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 20px;
  transition: background-color 0.3s ease, color 0.3s ease;
}

.theme-switch {
  position: absolute;
  top: 20px;
  right: 20px;
  display: flex;
  align-items: center;
  background-color: rgba(0, 0, 0, 0.05);
  padding: 6px 10px;
  border-radius: 20px;
  box-shadow: 0 0 5px rgba(0,0,0,0.1);
}

.theme-label {
  margin-left: 10px;
  font-size: 1.2rem;
}

.switch {
  position: relative;
  display: inline-block;
  width: 50px;
  height: 24px;
}

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

.slider {
  position: absolute;
  cursor: pointer;
  top: 0; left: 0;
  right: 0; bottom: 0;
  background-color: #ccc;
  transition: 0.4s;
  border-radius: 24px;
}

.slider:before {
  position: absolute;
  content: "";
  height: 18px; width: 18px;
  left: 3px; bottom: 3px;
  background-color: white;
  transition: 0.4s;
  border-radius: 50%;
}

input:checked + .slider {
  background-color: var(--accent-color);
}

input:checked + .slider:before {
  transform: translateX(26px);
}

.calculator {
  background-color: var(--display-bg);
  padding: 20px;
  border-radius: 15px;
  box-shadow: 0 0 20px rgba(0,0,0,0.1);
  max-width: 320px;
  width: 100%;
  transition: background-color 0.3s ease;
}

.display {
  background-color: var(--btn-bg);
  color: var(--font-color);
  padding: 15px;
  font-size: 2rem;
  border-radius: 10px;
  text-align: right;
  margin-bottom: 15px;
  min-height: 50px;
  transition: background-color 0.3s ease;
}

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

.btn {
  padding: 20px;
  font-size: 1.2rem;
  border: none;
  border-radius: 8px;
  background-color: var(--btn-bg);
  color: var(--btn-color);
  cursor: pointer;
  transition: background-color 0.2s ease, color 0.2s ease, transform 0.1s ease;
}

.btn:hover {
  background-color: var(--accent-color);
  color: #fff;
}

.btn:focus {
  outline: 2px solid var(--accent-color);
  outline-offset: 2px;
}

.btn:active {
  transform: scale(0.97);
}

.equal {
  grid-column: span 1;
  background-color: var(--equal-bg);
  color: var(--equal-color);
}

.equal:hover {
  filter: brightness(1.1);
}

.zero {
  grid-column: span 2;
}

footer {
  margin-top: 30px;
  font-size: 0.9rem;
  color: var(--font-color);
}

@media (max-width: 400px) {
  .calculator {
    padding: 15px;
  }

  .btn {
    padding: 16px;
    font-size: 1rem;
  }

  .display {
    font-size: 1.6rem;
  }
}