*
{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Lucida Sans', 'Lucida Sans Regular', 'Lucida Grande', 'Lucida Sans Unicode', Geneva, Verdana, sans-serif;
    scroll-behavior: smooth;
}

header
{
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    padding: 40px 100px;
    z-index: 1000;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: 0.5s;
}

header.sticky
{
    background: #fff;
    padding: 20px 100px;
    box-shadow: 0 5px 20px rgba( 0, 0, 0, 0.1);
}

header .logo 
{
    color: black;
    font-size: 24px;
    text-transform: uppercase;
    text-decoration: none;
    font-weight: 700;
    letter-spacing: 2px;
}

header.sticky .logo
{
    color: #111;
}

header ul
{
    position: relative;
    display: flex;
}

header ul li 
{
    position: relative;
    list-style: none;
}

header ul li a 
{
    position: relative;
    display: inline-block;
    font-size: 24px;
    font-weight: 700;
    margin: 0 15px;
    color: black;
    text-decoration: none;
}

header.sticky ul li a
{
    color: #111;
}

section
{
    padding: 100px;
}

/*calculator*/
 .jumbotron 
 { 
    width: 60%; 
    margin: auto; 
    text-align: center; 
} 
  
 #output 
{ 
    border: 2px solid black; 
    min-height: 60px; 
    text-align: right; 
    font-weight: bold; 
    font-size: 20px; 
} 
  
.btn 
{ 
    min-width: 120px; 
    border: 2px solid black; 
}