:root {
  --primary: #ff6b35;
  --primary-dack: #d85a2c;
  --bg-dark: #0f0f0f;
  --bg-card: #1a1a1a;
  --text: #ffffff;
  --text-muted: #a0a0a0;
  --accent: #00d4ff;
  --radius: 16px;
}

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

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(135deg, var(--bg-dark) 0%, #1a1a2e 100%);
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  padding: 20px;
}

#container {
  background: var(--bg-card);
  border-radius: var(--radius);
  width: 100%;
  max-width: 320px;
  padding: 24px;
  box-shadow:
    0 20px 60px rgba(0, 0, 0, 0.7),
    inset 0 1px 0 rgba(255, 255, 255, 0.1);
  border: 1px solid rgba(255, 255, 255, 0.05);
  backdrop-filter: blur(10px);
}

#display {
  width: 100%;
  padding: 20px;
  font-size: 2.5rem;
  font-weight: 500;
  border: none;
  background: rgba(255, 255, 255, 0.05);
  color: var(--text);
  margin-bottom: 20px;
  border-radius: 12px;
  text-align: right;
  outline: none;
  transition: all 0.3s ease;
  border: 1px solid rgba(255, 255, 255, 0.1);
  letter-spacing: 1px;
}

#display:focus {
  border-color: var(--accent);
  background: rgba(0, 212, 255, 0.08);
}

#key {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

button:nth-child(16),
button:nth-child(17) {
  background: linear-gradient(
    135deg,
    var(--primary) 0%,
    var(--primary-dack) 100%
  );
  border: none;
  color: white;
  grid-column: span 2;
}

button:nth-child(16):hover,
button:nth-child(17):hover {
  box-shadow: 0 12px 30px rgba(255, 107, 53, 0.4);
  transform: translateY(-3px);
}

button:nth-child(1),
button:nth-child(5),
button:nth-child(9),
button:nth-child(13) {
  color: var(--accent);
}

button {
  padding: 20px;
  border: none;
  border-radius: 12px;
  font-size: 1.2rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  color: var(--text);
  background: rgba(255, 107, 53, 0.2);
  border: 1px solid rgba(255, 107, 53, 0.3);
}

button:hover {
  background: rgba(255, 107, 53, 0.35);
  border-color: rgba(255, 107, 53, 0.6);
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(255, 107, 53, 0.2);
}

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