1. Create a variable called "score."
  2. Add to the score when the blue star touches the the blue android using "if/then," "change score by," and "touching" blocks.
  3. Make the score go down when the blue star touches the yellow android by duplicating the previous "if" block, changing the sprite name and changing the amount in the "change score by" block.
  4. Reset the score to 0 when the green flag is clicked using a "set score to" block.