Press SPACE and wait for the curve to finish. Then, press SPACE again! Hold Shift and Left Click the Flag to enter Turbo mode (fun and fast!). Use M to mute sounds, T for turbo sounds, and N for normal sounds. R to reset to the start! Scratch can only handle 8 iterations before the list stops working but, until then, enjoy!
Behold the Hilbert Curve, a very cool space filling curve! Hope you're having a great day!