Cat Program on Khan Academy

Hi, this is request for help post. I need help on Khan Academy with a certain program and if you're here to give help, this is the right post to comment on.

BTW this is my cat project on Khan.

Here's a picture of my problem. Click on it to see it in a better size.

You can see my problem on the bottom two lines of code. It wants me to put:

var cat_face_x; +=1;
var cat_face_y; +=1;

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I don't need the semi-colon in the middle of the variable. I don't know why he's asking for a semi. Consequently, I don't know how to fix it either