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

.CodeMirror {
	font-family: Inconsolata, monospace;
	height: 100%;
	border: 1px solid $ide-border-color;
}

.CodeMirror-linenumbers {
	padding-right: #{10 / $base-font-size}rem;
}

.CodeMirror-linenumber {
	width: #{35 / $base-font-size}rem;
}

.CodeMirror-lines {
	padding-top: #{25 / $base-font-size}rem;
}

.CodeMirror-line {
	padding-left: #{5 / $base-font-size}rem;
}

.CodeMirror-gutter-wrapper {
  right: 100%;
  top: 0;
  bottom: 0;
}

.CodeMirror-lint-marker-warning, .CodeMirror-lint-marker-error, .CodeMirror-lint-marker-multiple {
  background-image: none;
  width: 70px;
  position: absolute;
  height: 100%;
}

.CodeMirror-lint-message-error, .CodeMirror-lint-message-warning {
  background-image: none;
  padding-left: inherit;
}

.CodeMirror-lint-marker-warning {
  background-color: rgb(255, 190, 5);
}

.CodeMirror-lint-marker-error {
  background-color: rgb(255, 95, 82);
}

.CodeMirror-gutter-elt:not(.CodeMirror-linenumber) {
  opacity: 0.3;
  width: 70px !important;
  height: 100%;
  // background-color: rgb(255, 95, 82);
}

.CodeMirror-lint-tooltip {
  background-color: $light-modal-background-color;
  border: 1px solid $light-modal-border-color;
  border-radius: 2px;
  box-shadow: 0 12px 12px $light-shadow-color;
  font-family: Montserrat, sans-serif;
}