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

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
  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;
}

/* ===================================
           LAYOUT 1: MOBILE (default)
           1 column - stacked vertically
           =================================== */
.cards {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.card {
  background-color: #0f3460;
  border-radius: 16px;
  padding: 25px;
  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;
}

/* Layout indicator badges */
.layout-badge {
  display: inline-block;
  background-color: #4a90e2;
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 12px;
  margin-bottom: 15px;
}

/* ===================================
           LAYOUT 2: TABLET (768px and up)
           2 columns - side by side
           =================================== */
@media (min-width: 768px) {
  body {
    padding: 40px;
  }

  h1 {
    font-size: 36px;
  }

  .cards {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 25px;
  }
}

/* ===================================
           LAYOUT 3: DESKTOP (1024px and up)
           3 columns - full grid
           =================================== */
@media (min-width: 1024px) {
  .cards {
    grid-template-columns: repeat(3, 1fr);
  }
}

/* ===================================
           THEORY SECTION
           =================================== */
.theory {
  background-color: #0a0a1a;
  border-radius: 16px;
  padding: 25px;
  margin-top: 40px;
}

.theory h2 {
  color: #4a90e2;
  margin-bottom: 20px;
  font-size: 22px;
}

.theory h3 {
  color: #e94560;
  margin: 20px 0 10px;
}

.theory p {
  color: #ccc;
  line-height: 1.6;
  margin-bottom: 15px;
}

.theory ul {
  margin-left: 25px;
  color: #ccc;
  line-height: 1.8;
}

.theory code {
  background-color: #1a1a2e;
  padding: 2px 6px;
  border-radius: 4px;
  color: #82b1ff;
}

.breakpoint-box {
  background-color: #0f3460;
  border-radius: 12px;
  padding: 20px;
  margin: 20px 0;
}

.breakpoint-box h4 {
  color: #4a90e2;
  margin-bottom: 10px;
}

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

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