* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
span{
  display: inline-block;
}
button{
  cursor: pointer;
  background: transparent;
  border: none;
}
img {
  max-width: 100%;
}
video {
  width: 100%;
}
a {
  text-decoration: none;
}