:root {
  --bg: #1e1e2f;
  --text: #ffffff;
  --btn: #3e3e4e;
  --btn-hover: #5a5a6e;
  --btn-active: #7a7a8e;
  --title: #ffd700;
}

body.light {
  --bg: #f0f0f0;
  --text: #000000;
  --btn: #d0d0d0;
  --btn-hover: #c0c0c0;
  --btn-active: #a0a0a0;
  --title: #0057b7;
}

body {
  background: var(--bg);
  color: var(--text);
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  height: 100vh;
  margin: 0;
  font-family: 'Orbitron', sans-serif;
  transition: background 0.5s ease, color 0.5s ease;
}

.title {
  font-size: 2rem;
  color: var(--title);
  margin: 0;
}

.subtitle {
  margin: 5px;
  font-size: 0.9rem;
  opacity: 0.8;
}

.mode-switch {
  background: var(--btn);
  color: var(--text);
  padding: 10px 15px;
  border-radius: 8px;
  margin: 10px;
  cursor: pointer;
  border: none;
  transition: background 0.3s ease, transform 0.3s ease;
}

.mode-switch:hover {
  background: var(--btn-hover);
}

.mode-switch:active {
  transform: scale(0.95);
}

.calculator {
  background: var(--btn);
  padding: 20px;
  border-radius: 15px;
  box-shadow: 0 0 15px rgba(0, 0, 0, 0.5);
  max-width: 320px;
  width: 100%;
  transition: background 0.5s ease;
}

#display {
  width: 100%;
  height: 50px;
  font-size: 24px;
  text-align: right;
  margin-bottom: 10px;
  padding: 10px;
  border: none;
  border-radius: 10px;
  background: #222;
  color: white;
  font-family: inherit;
}

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

button {
  height: 50px;
  font-size: 18px;
  border: none;
  border-radius: 8px;
  background: var(--btn);
  color: var(--text);
  cursor: pointer;
  transition: background 0.2s ease, transform 0.2s ease;
}

button:hover {
  background: var(--btn-hover);
}

button:active {
  background: var(--btn-active);
  transform: scale(0.95);
}

#history {
  width: 100%;
  max-height: 100px;
  overflow-y: auto;
  font-size: 14px;
  background: rgba(0, 0, 0, 0.2);
  padding: 10px;
  border-radius: 8px;
  margin-top: 10px;
}

@media (max-width: 400px) {
  .buttons {
    grid-template-columns: repeat(3, 1fr);
  }
}