/* Reset some default styling */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  background-color: black;
  color: white;
  font-family: sans-serif;
  overflow-x: hidden;
}

img {
  display: block;
  max-width: 90%;
  margin: 30px auto;
  height: auto;
}

#overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: black;
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  z-index: 9999;
}

#overlay h1 {
  font-size: 2em;
  margin-bottom: 20px;
  text-align: center;
}

#startBtn {
  background: white;
  color: black;
  border: none;
  padding: 15px 30px;
  font-size: 1em;
  cursor: pointer;
  border-radius: 5px;
}

#startBtn:hover {
  background: #ddd;
}

#goTopBtn {
  position: fixed;
  bottom: 30px;
  right: 30px;
  background: white;
  color: black;
  border: none;
  padding: 10px 15px;
  cursor: pointer;
  border-radius: 4px;
  display: none;
}

#goTopBtn:hover {
  background: #ddd;
}