style.css

/* a minimalist set of CSS resets */

/* default to border-box */
html {
  box-sizing: border-box;
  font-size: 16px;
}

*, *:before, *:after {
  box-sizing: inherit;
}

/* adjust typography defaults */

body {
  margin: 1rem;
  font-family: sans-serif;
  line-height: 1.5;
  background-color: slategrey;
  color: white;
}
h1 {
  font-family: verdana, arial, sans-serif;
}
button{
  padding: 15px;
  border-radius: 15px;
  border: 5px solid purple;
}
#startBtn:hover {
  background: white;
}
#stopBtn:hover{
  background: white;
}
.hidden {
  display: none;
}
div#gameButtonArea > button {
  width:200px;
  height:200px;
  margin:5px;
  border: 2px solid purple;
}
#button1 {
    background: lightgreen;
}
#button1:active, #button1.lit {
    background:green;
}
#button2 {
    background: lightblue;
}
#button2:active, #button2.lit  {
    background:blue;
}
#button3 {
    background: pink;
}
#button3:active, #button3.lit  {
    background:red;
}
#button4 {
    background: lightyellow;
}
#button4:active, #button4.lit  {
    background:yellow;
}
#button5 {
    background: lightsalmon;
}
#button5:active, #button5.lit {
    background:orangered;
}
#button6 {
    background: mediumspringgreen;
}
#button6:active, #button6.lit {
    background:seagreen;
}
/* images and videos max out at full width */
img,
video {
  height: auto;
  max-width: 100%;
}