body {
    margin: 0;
    height: 100%;
}
html {
    height: 100%;
}

#board {
    height: 100%;
}

.redsquare {
    background-color: #FF0000;
}
.greensquare {
    background-color: #00FF00;
}
.bluesquare {
    background-color: #0000FF;
}

h1 {
    text-align: center;
}
#whichcolor {
    text-align: center;
}
.column {
    float: left;
    width: 50%;
    height: 100%;
}
  
/* Clear floats after the columns */
#board:after {
    content: "";
    display: table;
    clear: both;
}