body {
  margin: 0;
  padding: 0;
  width: 100vw;
  height: 100vh;
}

.window {
  width: 100%;
  height: 100%;
}

.start {
  position: absolute;
  width: 100vw;
  height: 100vh;
  background: url(1077beb3392431dc8f9a.png);
  background-size: cover;
  background-position: 50%, 50%;
  background-repeat: no-repeat;
  display: flex;
  justify-content: center;
  align-items: center;
}

.start button {
  cursor: pointer;
  background-color: #111;
  color: white;
  width: 200px;
  height: 200px;
  border-radius: 100%;
  border: none;
  font-size: 3em;
  text-transform: uppercase;
  font-weight: bold;
  transition: box-shadow .5s ease-in-out;
}

.start button:hover {
  box-shadow: 1px 1px 100px 5px orange;
}

.over {
  position: absolute;
  width: 100vw;
  height: 100vh;
  background: url(925f0358753fbf8e6405.png);
  background-size: cover;
  background-position: 50%, 50%;
  background-repeat: no-repeat;
  display: none;
}