body {
  font-family: "Segoe UI", sans-serif;
  margin: 0;
  background: #fafafa;
  color: #222;
}

header {
  background: #c62828;
  color: white;
  padding: 1.5rem 0;
  text-align: center;
}

h1 {
  margin: 0;
  font-size: 2rem;
}

.category {
  padding: 2rem 1rem;
  text-align: center;
}

.category h2 {
  color: #444;
  border-bottom: 2px solid #c62828;
  display: inline-block;
  padding-bottom: .3rem;
  margin-bottom: 1.5rem;
}

.worksheets {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 1.5rem;
}

.worksheet {
  background: white;
  border-radius: 10px;
  box-shadow: 0 2px 5px rgba(0,0,0,0.1);
  max-width: 260px;
  padding: 1rem;
  text-align: center;
  transition: transform 0.2s;
}

.worksheet:hover {
  transform: scale(1.03);
}

.thumbnail {
  width: 100%;
  border-radius: 8px;
  cursor: pointer;
}

.download-btn {
  display: inline-block;
  background: #c62828;
  color: white;
  text-decoration: none;
  padding: 0.5rem 1rem;
  border-radius: 8px;
  margin-top: 0.5rem;
  transition: background 0.2s;
}

.download-btn:hover {
  background: #a81f1f;
}

.downloads {
  display: block;
  margin-top: .5rem;
  color: #777;
  font-size: 0.9rem;
}

.lightbox {
  display: none;
  position: fixed;
  z-index: 100;
  left: 0; top: 0;
  width: 100%; height: 100%;
  background: rgba(0,0,0,0.8);
  justify-content: center;
  align-items: center;
}

.lightbox img {
  max-width: 90%;
  max-height: 90%;
  border-radius: 10px;
}

footer {
  background: #333;
  color: white;
  text-align: center;
  padding: 1rem;
  margin-top: 2rem;
}

@media (max-width: 768px) {
  .worksheets {
    flex-direction: column;
    align-items: center;
  }
}