src/app.css

/* src/app.css */
:root {
  --bg-color: #f5f5f5;
  --calculator-bg: #1a1a1a;
  --display-bg: #2a2a2a;
  --button-bg: #3a3a3a;
  --button-hover: #4a4a4a;
  --operator-bg: #ff9500;
  --operator-hover: #ffaa33;
  --function-bg: #505050;
  --function-hover: #606060;
  --text-color: #ffffff;
  --text-secondary: #cccccc;
  --border-radius: 12px;
  --button-radius: 8px;
  --transition: all 0.2s ease;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background-color: var(--bg-color);
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 20px;
}

.calculator {
  background-color: var(--calculator-bg);
  border-radius: var(--border-radius);
  padding: 20px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
  width: 100%;
  max-width: 340px;
}

.display {
  background-color: var(--display-bg);
  border-radius: var(--border-radius);
  padding: 20px;
  margin-bottom: 20px;
  text-align: right;
  min-height: 80px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  word-wrap: break-word;
  word-break: break-all;
}

.display-text {
  font-size: 2.5rem;
  font-weight: 300;
  color: var(--text-color);
  line-height: 1.2;
}

.error {
  font-size: 0.875rem;
  color: #ff6b6b;
  margin-top: 5px;
}

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

button {
  background-color: var(--button-bg);
  color: var(--text-color);
  border: none;
  border-radius: var(--button-radius);
  font-size: 1.5rem;
  padding: 20px;
  cursor: pointer;
  transition: var(--transition);
  font-weight: 300;
}

button:hover {
  background-color: var(--button-hover);
  transform: translateY(-1px);
}

button:active {
  transform: translateY(0);
}

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

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

button.operator {
  background-color: var(--operator-bg);
  font-size: 1.75rem;
  font-weight: 400;
}

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

button.equals {
  background-color: var(--operator-bg);
  grid-column: 3 / 5;
}

button.equals:hover {
  background-color: var(--operator-hover);
}

button.zero {
  grid-column: 1 / 3;
}

@media (max-width: 480px) {
  .calculator {
    padding: 15px;
  }
  
  .display {
    padding: 15px;
    min-height: 70px;
  }
  
  .display-text {
    font-size: 2rem;
  }
  
  button {
    font-size: 1.25rem;
    padding: 15px;
  }
}