Your #black-hat selector should have a border-top-color property set to transparent.

#black-hat {
    width: 0;
    height: 0;
    border-style: solid;
    border-width: 150px 0 0 300px;
    border-top-color: transparent;
    border-right-color: transparent;
    border-bottom-color: transparent;
    border-left-color: rgb(45, 31, 19); /* false-black */
    position: absolute;
    top: -150px;
    left: 0;

What exactly do you need help with? Which challenge are you working on?

I’ve edited your post for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.

You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.

See this post to find the backtick on your keyboard.
Note: Backticks (`) are not single quotes (’).