.container {
  position: relative;
  margin: 20px auto;
  padding: 20px;
  border-radius: 16px;
  font-family: 'Poppins', sans-serif;
  text-align: center;
  max-width: 900px;
  background: #121212; /* Ultra-dark background */
  color: #e0e0e0; /* Soft white text for readability */
  box-shadow: 0 12px 35px rgba(0, 0, 0, 0.3);
  z-index: 1;
}

/* Dark gradient border (deep blue + teal green) */
.container::before {
  content: '';
  position: absolute;
  top: -4px;
  left: -4px;
  right: -4px;
  bottom: -4px;
  z-index: -1;
  border-radius: 20px;
  background: linear-gradient(135deg, #003366, #005544); /* Dark blue to dark green */
}

.container h1 {
  font-size: 40px;
  font-weight: 800;
  color: #222;
  background: linear-gradient(90deg, #0d6efd, #20c997);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  text-align: center;
  margin-bottom: 30px;
  letter-spacing: 1.5px;
  text-shadow: 1px 1px 3px rgba(0,0,0,0.1);
  padding: 10px 0;
  border-bottom: 3px solid #0d6efd;
  display: inline-block;
}

.second-button {
  background: #3b82f6;
  color: white;
  padding: 0.6rem 1rem;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  margin-top: 0.5rem;
}

.second-button:hover {
  background-color: #2563eb;
  box-shadow: 0 8px 18px rgba(0, 0, 0, 0.2);
  transform: translateY(-2px);
}

.controls {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-bottom: 2rem;
}

label {
  display: flex;
  flex-direction: column;
  font-size: 0.95rem;
}

input[type="number"], input[type="checkbox"] {
  margin-top: 0.5rem;
  padding: 0.4rem;
  font-size: 1rem;
  border: 1px solid #ccc;
  border-radius: 6px;
}

.preview {
  border: 2px dashed #ccc;
  padding: 1rem;
  border-radius: 8px;
  background: #fff;
}

.grid-container {
  display: grid;
  margin-top: 1rem;
}

.grid-item {
  background: #d1d5db;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
  font-size: 1rem;
}

.css-output {
  background: #111827;
  color: #d1fae5;
  padding: 1rem;
  border-radius: 8px;
  margin-top: 1rem;
  overflow-x: auto;
  white-space: pre-wrap;
}