p5.js-web-editor/client/styles/layout/_fullscreen.scss

.fullscreen-preview {
  display: flex;
  width: 100%;
  height: 100%;
  flex-flow: column;
}

.fullscreen-preview__title {
  width: 100%;
}

.fullscreen-preview__frame-wrapper {
  width: 100%;
  flex: 1 0 0%;
  position: relative;
}