Add square buildings steps to building chapter

data/core.yaml

@@ -876,6 +876,7 @@ en:
       close: "**Hit escape, or click the {button} button to close the feature editor**"
       rightclick_building: "**Right-click to select the building you created.**"
       square_building: "The house that you just added will look even better with perfectly square corners. **Click on the {button} button to square the building shape.**"
+      retry_square: "You didn't click the Square button. Try again."
       done_square: "See how the corners of the building moved into place?  Let's learn another useful trick."
       add_tank: "Let's trace this circular storage tank. **Click the {button} Area button to add a new area.**"
       start_tank: "Don't worry, you won't need to draw a perfect circle. Just draw an area inside the tank that touches its edge. **Click or press spacebar to place a starting node on the edge of the tank.**"
@@ -884,6 +885,7 @@ en:
       choose_tank: "**Choose {name} from the list.**"
       rightclick_tank: "**Right-click to select the storage tank you created.**"
       circle_tank: "**Click on the {button} button to make the tank a circle.**"
+      retry_circle: "You didn't click the Circularize button. Try again."
       play: "Great Job! Try tracing a few more buildings. **When you are ready to continue to the next chapter, click '{next}'.**"
     startediting:
       title: "Start Editing"