:root {
  --bg: #0a0e27;
  --surface: rgba(255,255,255,.04);
  --surface-hover: rgba(255,255,255,.08);
  --border: rgba(255,255,255,.06);
  --border-hover: rgba(255,255,255,.12);
  --text: #ffffff;
  --text-muted: rgba(255,255,255,.45);
  --text-body: rgba(255,255,255,.65);
  --accent: #00d9ff;
  --accent-2: #7c3aed;
  --radius: 0.5rem;
}

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

body {
  font-family: 'Inter', sans-serif;
  color: var(--text);
  -webkit-font-smoothing: antialiased;
}

.calculator-container {
  width: 100%;
  max-width: 380px;
}

.calculator-card {
  background: var(--surface);
  backdrop-filter: blur(20px);
  border: 1px solid var(--border);
  border-radius: calc(var(--radius) * 2);
  padding: 1.5rem;
  box-shadow: 0 20px 60px rgba(0,0,0,.4), 0 0 0 1px rgba(255,255,255,.02);
}

.display-container {
  background: rgba(0,0,0,.2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  min-height: 120px;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  align-items: flex-end;
  gap: 0.5rem;
}

.expression {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 0.875rem;
  color: var(--text-muted);
  min-height: 1.25rem;
  letter-spacing: 0.02em;
}

.display {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 2.5rem;
  font-weight: 600;
  color: var(--text);
  letter-spacing: -0.02em;
  word-break: break-all;
  text-align: right;
  line-height: 1.2;
}

.button-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.75rem;
}

.btn {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1.25rem;
  font-weight: 500;
  padding: 1.25rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
  transition: all 0.2s ease;
  outline: none;
  -webkit-tap-highlight-color: transparent;
}

.btn:hover {
  background: var(--surface-hover);
  border-color: var(--border-hover);
  transform: translateY(-1px);
}

.btn:active {
  transform: translateY(0);
}

.btn-number {
  font-weight: 400;
}

.btn-zero {
  grid-column: span 2;
}

.btn-function {
  color: var(--accent);
  font-weight: 600;
}

.btn-operator {
  background: rgba(0, 217, 255, 0.08);
  color: var(--accent);
  border-color: rgba(0, 217, 255, 0.15);
  font-weight: 600;
}

.btn-operator:hover {
  background: rgba(0, 217, 255, 0.15);
  border-color: rgba(0, 217, 255, 0.25);
  box-shadow: 0 0 20px rgba(0, 217, 255, 0.2);
}

.btn-equals {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border-color: transparent;
  color: var(--text);
  font-weight: 700;
  box-shadow: 0 4px 20px rgba(0, 217, 255, 0.2);
}

.btn-equals:hover {
  box-shadow: 0 6px 30px rgba(0, 217, 255, 0.35);
  transform: translateY(-2px);
}

@media (max-width: 480px) {
  .calculator-card {
    padding: 1.25rem;
  }
  
  .display {
    font-size: 2rem;
  }
  
  .btn {
    padding: 1rem;
    font-size: 1.125rem;
  }
  
  .button-grid {
    gap: 0.625rem;
  }
}