Press the keys 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, a and b to change the invisible sprite's costume. Up arrow shows the sprite and down arrow hides it. Hold shift while clicking the flag to activate turbo mode. Otherwise click the flag and then wait to see what the current sprite is.
Thanks to Julian from Greytown Code Club for lending me his book. Thanks to Carol Vorderman for writing the book Computer Coding Projects For Kids Using Scratch.
