body {
  margin: 0;
  background: #000;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  font-family: sans-serif;
}

.gallery {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  padding: 10px;
  justify-content: center;
}

.gallery img {
  width: 150px;
  height: auto;
  cursor: pointer;
  border-radius: 5px;
  transition: transform 0.2s;
}

.gallery img:hover {
  transform: scale(1.05);
}

#fullscreen {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: black;
  justify-content: center;
  align-items: center;
}

#fullscreen img {
  max-width: 100%;
  max-height: 100%;
}

#back-btn {
  position: absolute;
  top: 15px;
  left: 15px;
  background: rgba(0,0,0,0.5);
  border: none;
  color: white;
  font-size: 18px;
  padding: 10px 15px;
  border-radius: 5px;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.3s;
}

#back-btn.show {
  opacity: 1;
}