Step 1.  Under the CONTROL category, add when Flag clicked


 

Step 2.  Connect the Forever script


 

Step 3.  Click on the MOTION category.  Put move 10 steps into the Forever Loop


 

Step 4. Put if on edge, bounce anywhere into the forever loop


 

Step 5. Try clicking on the Green flag to see what happens.  The cat goes back and forth but flips upside down.  To stop this, click on the left-right arrow next to the small Sprite icon at the top of the screen.  If you hover your mouse over it, it will say "only face left-right".  The one it starts on allows 360 degree flips, and the bottom one does not allow flipping at all.


 

Step 6.  Switch to the LOOKS category.  Move next costume anywhere into the Forever loop.


 

Step 7.  You're DONE!  Click on the Green flag at the top right to watch the Cat run back and forth.