body{
  margin: 0;
  padding: 0;
}
.container{
  text-align: center;
  margin-top: 360px;
}
.btn{
  border: 1px solid #3498db;
  background: none;
  padding: 10px 20px;
  font-size: 20px;
  font-family: "montserrat";
  cursor: pointer;
  margin: 10px;
  transition: 0.8s;
  position: relative;
  overflow: hidden;
}

#but{
font-size: 15px;
 padding: 2px 10px;
border-radius: 8px;

}

#but2{
font-size: 15px;
 padding: 2px 10px;
border-radius: 8px;

}

#add{
border-radius: 8px;
background: rgba(0,255,0,0.5);

}
.btn1,.btn2{
  color: #3498db;
}
.btn3,.btn4{
  color: #fff;
  text-align: center;
}
.btn1:hover,.btn2:hover{
  color: #fff;
}
.btn3:hover,.btn4:hover{
  color: #3498db;
}
.btn::before{
  content: "hola";
  position: absolute;
  left: 0;
  width: 100%;
  height: 0%;
  background: #3498db;
  z-index: -1;
  transition: 0.8s;
}
.btn1::before,.btn3::before{
  top: 0;
  border-radius: 0 0 50% 50%;
}
.btn2::before,.btn4::before{
  bottom: 0;
  border-radius: 50% 50% 0 0;
}
.btn3::before,.btn4::before{
  height: 180%;
}
.btn1:hover::before,.btn2:hover::before{
  height: 180%;
}
.btn3:hover::before,.btn4:hover::before{
  height: 0%;
}