h1{
    background-color: rgb(104, 22, 22);
    color: rgb(255, 0, 0);
    text-align: center;
}
/* 2) Pseudo classes (:)*/
h1:hover{
    color: rgb(0, 255, 34);
    background-color: black;

}
p:hover{
color: greenyellow;
background-color: black;
}

.inp:focus{
    background-color: aquamarine;
}
/* h.w= usage of focus */

.sub:active{
    background-color: chartreuse;
}
a:visited{
    background-color: red;
}
a:link{
    background-color: rgb(0, 208, 255);
}
#back:visited{
    background-color: rgb(0, 170, 255);
}
#back:link{
    background-color: rgb(255, 240, 23);
}
.container p:nth-child(2n+1){
    background-color: firebrick;
    color: #ffffff;
}
input:focus{
  outline: 2px solid green;
  background-color: rgb(194, 48, 48);
}

input:valid{
  background-color: greenyellow;
}

input:invalid{
  background-color: red;   
}