Clicking on the little black square again makes the cursor disappear

When Pixel.js first opens, the user needs to click on the black square in the top left corner to open up the tutorial pop-up and then proceed to correction. If you start correcting and then click on the black square again, the page "resets," so all the layers disappear. This is fine, because clicking on the square one more time makes the tutorial pop-up reappear, and once you close that window your layers reappear. However, at that point dragging your cursor over the image makes the cursor disappear, and I haven't found a way to get it back. The only solution I've found is to close the page and start again, which means that your work is effectively lost.

Demo, which starts from when the Pixel.js window opens:

Uploading Pixel cursor disappearing.mov…

Does the black square serve any function once the user has started correcting? If not, I feel like it could just disappear after the user first clicks on it.