It's really simple. Click on the jar of blocks to take out a block, and drag it to scratch cat's mouth to feed it to scratch cat. You can also click on scratch cat. That's it for now! To change the backdrop, press space... In this update: -New backdrop ...and don't spam scratch cat. I know you will, out of curiosity, but still, don't. Or you might get a...well...not-so-small issue.
