/*Document*/
*
{
    margin: 0;
    padding: 0;
    box-sizing: border-box
}

/*Browser window*/
body
{
   width: 100vw;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

/*Canvas*/
#canvas1
{
    width: 800px;
    height: 500px;
    border: 4px solid black;
    background: linear-gradient(to bottom, lightblue, darkblue, black);
}