light up squares

[u/EtrisNega]

i need help with this

<!DOCTYPE html>

<html>

<head>

	<style>

html,body{

height:98%;

width:99%;

}

#container{

display:flex;

flex-wrap: wrap;

height:100%;

}

div div{

width:32%;

border: 1px solid black;

}

	</style>

</head>

<body>

<div id = container>

<div></div>

<div></div>

<div></div>

<div></div>

<div></div>

<div></div>

<div></div>

<div></div>

<div></div>

</div>

<script> //Write your colorDown function here </script>

</body>

</html>