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

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: #1a1a2e;
  color: #eee;
  padding: 20px;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
}

h1 {
  font-size: 28px;
  text-align: center;
  margin-bottom: 10px;
}

.subtitle {
  text-align: center;
  color: #aaa;
  margin-bottom: 40px;
  font-size: 14px;
}

/* ===================================
           MOBILE FIRST (default)
           Cards stack VERTICALLY (column)
           =================================== */
.cards {
  display: flex;
  flex-direction: column; /* ← Mobile: stack vertically */
  gap: 20px;
}

.card {
  background-color: #0f3460;
  border-radius: 16px;
  padding: 25px;
  text-align: center;
  transition: transform 0.3s ease;
}

.card:hover {
  transform: translateY(-5px);
}

.card-icon {
  font-size: 48px;
  margin-bottom: 15px;
}

.card h3 {
  font-size: 20px;
  margin-bottom: 10px;
  color: #4a90e2;
}

.card p {
  font-size: 14px;
  color: #aaa;
  line-height: 1.5;
}

/* ===================================
           DESKTOP (min-width: 768px)
           Cards become HORIZONTAL (row)
           =================================== */
@media (min-width: 768px) {
  body {
    padding: 40px;
  }

  h1 {
    font-size: 36px;
  }

  .cards {
    flex-direction: row; /* ← Desktop: horizontal row */
    flex-wrap: wrap; /* Wrap to next line if needed */
  }

  .card {
    flex: 1 1 calc(33.333% - 20px);
    min-width: 250px;
  }
}

/* ===================================
           CODE DISPLAY
           =================================== */
.code-block {
  background-color: #0a0a1a;
  padding: 20px;
  border-radius: 12px;
  font-family: "Courier New", monospace;
  font-size: 13px;
  color: #82b1ff;
  overflow-x: auto;
  margin-top: 40px;
}

.explanation {
  background-color: #0f3460;
  border-radius: 12px;
  padding: 20px;
  margin-top: 30px;
}

.explanation h3 {
  color: #4a90e2;
  margin-bottom: 15px;
}

.explanation ul {
  margin-left: 20px;
  line-height: 1.8;
}

footer {
  text-align: center;
  margin-top: 40px;
  padding: 20px;
  color: #666;
  font-size: 14px;
}