:root
{
--green: #00875C;
--light-green: #BFF0C3;
--lime: #89C000;
--dark-lime: #74A300;
--turquoise: #00837C;
}
body
{
  background: var(--green);
}

header, section, div
{
  border:double 6px; padding:20px; margin:6px;
}

header, .subcolor, .button
{
  background:white;
  text-align:center;
}
section
{
  background: var(--light-green);
}

#green
{
  color: var(--green);
}
#lime
{
  color: var(--dark-lime);
}
#turquoise
{
  color: var(--turquoise);
}

#problem1
{
color: black;
background:lime;
border:double 6px black; padding:10px;
}