style.css

body {
    background-color: lightgray;
}

#annc {
    display: block;
    width: 50%;
    height: 400px;
}
kbd {
    background-color: whitesmoke;
    border-color: rgb(183, 183, 183);
    border-style: solid;
    border-width: 1px;
}
.submenu {
    padding-left: 20px;
    display: none;
}


/* tree stuffs */
#options ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    user-select: none;
}
.caret {
    cursor: pointer;
    user-select: none;
    font-weight: bold;
}
.caret::after {
    content: "\25B6";
    color: black;
    display: inline-block;
    margin-left: 6px;
    font-size: 0.8em;
    transform: rotate(90deg);
}
.caret-down::after {
    transform: unset;
  }
.nested {
    display: block;
}
.active {
    display: none;
}

/* option sections stuffs */
.options-section {
    border-left: 4px solid;
    border-radius: 4px;
}
.options-section li {
    padding-left: 10px;
    display: block;
    margin-top: 1em;
    margin-bottom: 1em;
    margin-left: 0;
    margin-right: 0;
}
.options-section::first-line { /* bold first line of options section */
    font-weight: bold;
}
.toggleable{cursor: pointer;}
/* define colors for options sections */
#general-options {border-color: slateblue;}
#segments {border-color: palevioletred;}
#customization {border-color: teal;}