Watch the Glitch Cats glitch scratch use left, right, and up arrow keys to move the player This is all caused by actual glitching. It is not a simulation. For the best effect from the beginning, if you have the Scratch Addons Extension and you tick the Running Block Border addon, click See Inside. The amount of code inside will cause the Running Block Border to go crazy. Another reason for the lag is a Run without Screen Refresh custom block with a Repeat Until inside, which causes a big lag, no matter what.