:root {
  --color-background: #1a1a1a;
  --color-display: #333333;
  --color-button: #282828;
  --color-button-hover: #404040;
  --color-operator: #ff4d4d;
  --color-operator-hover: #cc3333;
  --color-text: #fff;
  --color-text-secondary: #b3b3b3;
}

body {
  margin: 0;
  padding: 0;
  font-family: Arial, Helvetica, sans-serif;
  font-size: 16px;
  line-height: 1.5;
  color: var(--color-text);
  background-color: var(--color-background);
}

.calculator {
  height: 95vh;
  max-width: 30%;
  margin: 50px auto;
  padding: 20px 20px 40px;
  background-color: #1f1f1f;
  border-radius: 20px;
  box-shadow: 0px 0px 10px rgba(0, 0, 0, 0.2);
  position: relative;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.calculator-display {
  width: 100%;
  height: 100px;
  margin-bottom: 20px;
  padding: 10px;
  background-color: var(--color-display);
  border-radius: 5px;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  font-size: 3rem;
  font-weight: bold;
  color: var(--color-text);
  box-shadow: 0px 2px 5px rgba(0, 0, 0, 0.1);
  position: relative;
}

.calculator-display:before {
  content: '';
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(to bottom, rgba(255, 255, 255, 0.1), rgba(255, 255, 255, 0.05));
  z-index: 1;
}

.calculator-keys {
  width: 100%;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 20px;
}

.button {
  height: 70px;
  border: none;
  border-radius: 10px;
  background-color: var(--color-button);
  color: var(--color-text);
  font-size: 24px;
  font-weight: bold;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s ease-in-out;
  box-shadow: 0px 2px 5px rgba(0, 0, 0, 0.1);
  position: relative;
  z-index: 1;
}

.button:hover {
  background-color: var(--color-button-hover);
  transform: translateY(-5px);
  box-shadow: 0px 8px 15px rgba(0, 0, 0, 0.2);
}

.clear {
  grid-column: span 2;
  background-color: var(--color-operator);
  color: var(--color-text);
}

.clear:hover {
  background-color: var(--color-operator-hover);
  transform: translateY(-5px);
  box-shadow: 0px 8px 15px rgba(0, 0, 0, 0.2);
}

.backspace {
  background-color: var(--color-operator);
  color: var(--color-text);
}

.backspace:hover {
  background-color: var(--color-operator-hover);
  transform: translateY(-5px);
  box-shadow: 0px 8px 15px rgba(0, 0, 0, 0.2);
}

.operator {
  background-color: var(--color-operator);
  color: var(--color-text);
}

.operator:hover {
  background-color: var(--color-operator-hover);
  transform: translateY(-5px);
  box-shadow: 0px 8px 15px rgba(0, 0, 0, 0.2);
}

.equal {
  background-color: var(--color-operator);
  color: var(--color-text);
}

.equal:hover {
  background-color: var(--color-operator-hover);
  transform: translateY(-5px);
  box-shadow: 0px 8px 15px rgba(0, 0, 0, 0.2);
}

.number {
  background-color: var(--color-button);
}

.number:hover {
  background-color: var(--color-button-hover);
  transform: translateY(-5px);
  box-shadow: 0px 8px 15px rgba(0, 0, 0, 0.2);
}

.zero {
  grid-column: span 2;
}

.decimal {
  background-color: var(--color-button);
}

.decimal:hover {
  background-color: var(--color-button-hover);
  transform: translateY(-5px);
  box-shadow: 0px 8px 15px rgba(0, 0, 0, 0.2);
}

@media only screen and (min-width: 768px) {
  .calculator-keys {
    max-width: 600px;
  }

  .button {
    height: 80px;
    font-size: 1.5rem;
  }

  .calculator-display {
    font-size: 4rem;
  }
}