nav{
  position:fixed;
  width:100%;
  max-width:75%;
  display:block;
  text-align:center; 
  padding-top:.5%;
  padding-bottom:.5%;
  margin: 0 auto;
  background-color: black;
  color:white;
}

h1{
  margin-top:20px;
  font-weight:bold;
}

h4{
  font-weight: bold;
  margin-left:1em;
}

p{
  font-family:helvetica;
  margin-top: 1em;
  margin-left:2em;
}

a{
  margin: 1em;
  color:white;
}

#blastar{
  background-image: url(https://cdn.vox-cdn.com/thumbor/UAJfqPoDEov5DeZohKvG4xl7k2I=/0x3:742x420/1600x900/cdn.vox-cdn.com/uploads/chorus_image/image/46503568/CHB34_mUIAAGmtV.0.0.png);
  background-size:100%;
  background-position: center;
  background-repeat: no-repeat;
  color:white;
  background-image: 0 auto;
}

#spacex{
  background-image:url(https://cnet4.cbsistatic.com/img/SdGF2VHyFVfx-t8jC9dAs9AedOA=/1600x900/2015/02/23/1d934701-ef55-4166-956c-5d38acf6102e/falcon-9-dscovr-launch.jpg);
  background-size:cover;
  background-position:center;
  color:white;
}

#tesla{
  background-image: url(https://www.tesla.com/sites/default/files/images/software_update.jpg);
  background-size:cover;
  background-position:center;
  color:white;
}

#transbox{
  background: rgba(0,0,0,0.45);
  box-sizing: content-box;
  padding-top:10px;
  padding-right: 10px;
  margin-left:15px;
  margin-bottom:30px;
}

@media (max-width: 550px){
  nav{
    max-width: 85%;
  }

  #blastar{
    background-size: 230%;
  }

}