treehouse/static/css/page/index.css

.index\:hobby-corners {
    &>li {
        margin: var(--8px) 0px;

        &>details {
            border-top: var(--4px) solid var(--section-color);
        }

        &>details>summary {
            position: relative;
            overflow: clip;
            box-sizing: border-box;

            border-top-left-radius: 0;
            border-top-right-radius: 0;

            &>th-bb>.icon {
                opacity: 100%;
            }

            & .background-icon {
                position: absolute;
                right: calc(var(--button-bar-icon-size) * 2);
                bottom: 0;
                color: var(--text-color);
                opacity: 40%;

                width: 6.85rem;
                height: auto;

                pointer-events: none;
            }
        }
    }

}

#index\:programming {
    --section-color: var(--liquidex-brand-red);
}

#index\:design {
    --section-color: var(--liquidex-brand-yellow);
}

#index\:music {
    --section-color: var(--liquidex-brand-green);
}

#index\:games {
    --section-color: var(--liquidex-brand-blue);
}