Click the green flag to begin, and then click the screen to cycle through the costumes. The last one is the best ;)
Thanks to @haruni459 for the original project Slit animation: https://scratch.mit.edu/projects/711427182 In this remix, I have removed the sliders, and instead change the step variable automatically using a sine function. I have also added many costumes. The last one was drawn (traced) by yours truly. And I added music (made in BeepBox).