body {
  background-image: url(../images/1bgarab4u.jpg);
  background-repeat: no-repeat;
  background-attachment: fixed;  
  background-size: cover;
  font-family:Roboto, Geneva, sans-serif;
  font-size:18px;
  margin: auto;
 }

@media (max-width: 700px) 
{
   body
   {
       font-size: 15px; 
   }
}

@media (min-width: 900px) 
{
   body
   {
       font-size: 30px; 
   }
}

/* Make content area fill the entire browser window */
html,
.fullscreen {
  display:block;
  height: 100%;
  width: 100%;
}


/* Center the content in the browser window */
main {
max-width: 900px;
 margin: auto;
  }

.center {
 display: block;
 position: relative;
}

.container {
  display: grid;
  position: relative;
  padding: 10px 10px 10px 10px; 
  grid-gap: 1.5rem;
  grid-template-columns: repeat(auto-fill, minmax(min(15rem, 100%), 1fr));  
  list-style: none;
}

.card {
  background: #0a003c;
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.19), 0 6px 6px rgba(0, 0, 0, 0.23);
  border-radius: 10px;
  padding: 10px 3px 5px 3px;
}

.button {
  background-color: #0a003c;
  border: none;
  color: white;
  padding: 16px 32px;
  text-align: center;
  font-size: 15px;
  opacity: 1;
  transition: 0.3s;
  display: inline-block;
  text-decoration: none;
  cursor: pointer;
}


.buttonlesson {
width: 100%;}

.buttonlesson:hover {background-color: #2e3192}

.buttonback {
  position: fixed;
  z-index: 99;
  right: 0;  
  width: 150px;
  height: auto;
  bottom: 0.5rem;
} 

.imgbuttonback {
  width: 100%;
  height: auto;
}