Lets talk about variables; have you noticed how you cant see the values inside other sprites, such as X or Y or Costume. You have to share them with a variable then tell the other sprites that the variable has changed. Check the comments in the Backdrop to try out some ideas.
Variables are one of three things that all computer programs; those are Store information ( in the form of variables ) Iterate on information ( in the form of loops ) Decide on information ( in the form of conditions and operators )