style.css

body {
     margin: 0px 0 0;
     padding: 50px;
     font-family: 'Source Sans Pro', sans-serif;
     display: flex;
     justify-content: center;
     align-items: center;
}
.container {
     
     padding: 0;
     margin: auto;
     display: grid;
     margin: 5px 15px;
     gap: 20px;
     width: 100%;
     box-shadow: 0 10px 10px rgba(0,0,0,.1);
     /* text-align: center; */
}
.nav{
     text-align: center;
}
.nav a{

     font-family: sans-serif;
     text-decoration:none;
}

.btn{
     font-size: 1em;
     background: blue;
     color: white;
     border: white 0.2rem solid;
     border-radius: 0.5rem;
     padding: 0.8rem 35rem;
     box-shadow: 0 10px 10px rgba(0,0,0,.1);
     margin-top: 1rem;
}

.tiga img{
     display: block;
     margin-left: auto;
     margin-right: auto;
}

.isi{
     background: rgb(0, 134, 123);
     color: white;
     border: white 1.2rem solid;
     border-radius: 0.5rem;
     padding: 0.8rem 20rem;
     margin-top: 1rem;
     
}

.rumusS{
     text-align: center;
}

.pengertian{
     margin-left: 25px;
}
h1{
     text-align: center;
}
.input{
     text-align: center;
}
.button{
     font-size: 1em;
     background: blue;
     color: white;
     border: white 0.2rem solid;
     border-radius: 0.5rem;
     padding: 0rem 3rem;
     box-shadow: 0 10px 10px rgba(0,0,0,.1);
     margin-top: 1rem;
     text-align: center;
}
.center{
     display: flex;
     justify-content: center;
     align-items: center;
     color: blue;

}


.jg img{
     display: block;
     margin-left: auto;
     margin-right: auto;
}