#content{
  position: relative;
  background-color: transparent; 
}

#content::after {
  content: "";  
  background-size:     cover;                        
  background-repeat:   no-repeat;
  background-position: center center;              

  opacity: 1.0;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  position: absolute;
  z-index: -1;   
}

#exercise{  
  max-width: 900px; 
  min-height: 800px; 
}

#exercise span{ 
  border-radius: 4px;
  padding-left:4px;
  padding-right:4px;
}

#exercise .solved{
  color:red;
  border-radius: 0px;
  padding-left:0px;
  padding-right:0px;  
}

#exercise #joke{
  text-align: left;
  border-radius:4px;
  cursor: crosshair;
  font-size: 24px;
  line-height: 130%;  
  padding: 10px;
  margin:20px 0px;  
  background-color: white;
  box-shadow: 0px 0px 32px 0px rgba(0,0,0,0.2);
}

#exercise .ammo{
  width:25px;
}

#exercise .target{
  width:70px;
}

#exercise .disabled{
  background-color: gray;
  color:white;
}

#exercise #explanation{
  font-size: 18px;
  line-height: 28px;
  text-align: center;
  margin:10px;
  margin-top: 20px;
  border-radius: 3px;
  padding: 20px;
  background-color: white;
  display:none;
  box-shadow: 0px 0px 32px 0px rgba(0,0,0,0.1);
}

#exercise #explanation.whiteScreen{
  box-shadow: 0px 0px 32px 0px rgba(0,0,0,0);
}

/********************** WHITE SCREEN *****************************/
#exercise.whiteScreen{ 
  padding: 0px 10px;
}

#exercise.whiteScreen #joke{ 
  box-shadow: 0px 0px 32px 0px rgba(0,0,0,0); 
}

/********************** MOBILE SCREEN *****************************/
@media screen and (max-width: 550px) {
  #exercise #sentence{
    padding: 10px;
    margin:30px 20px;    
    font-size: 20px;
  }
}