p5.js-web-editor/client/styles/components/_sidebar.scss

.sidebar__header {
  padding: #{10 / $base-font-size}rem #{6 / $base-font-size}rem;
  display: flex;
  justify-content: space-between;
  border-top: 1px solid $ide-border-color;
}

.sidebar__title {
  font-size: #{12 / $base-font-size}rem;
  display: inline-block;
}

.sidebar__add {
  cursor: pointer;
}

.sidebar__file-list {
  border-top: 1px solid $ide-border-color;
}

.sidebar__file-item {
  font-size: #{12 / $base-font-size}rem;
  padding: #{8 / $base-font-size}rem #{20 / $base-font-size}rem;
  color: $light-inactive-text-color;
  cursor: pointer;
  &--selected {
    background-color: $ide-border-color;
  }
}