Changed 'fieldInnerCoords' to 'fieldCoords' to match image and text

Author: simmayor

2-ui/2-events/01-introduction-browser-events/04-move-ball-field/solution.md

@@ -33,7 +33,7 @@ We have `event.clientX/clientY` -- window-relative coordinates of the click.
 To get field-relative `left` coordinate of the click, we can substract the field left edge and the border width:
 
 ```js
-let left = event.clientX - fieldInnerCoords.left - field.clientLeft;
+let left = event.clientX - fieldCoords.left - field.clientLeft;
 ```
 
 Normally, `ball.style.position.left` means the "left edge of the element" (the ball). So if we assign that `left`, then the ball edge would be under the mouse cursor.
@@ -43,7 +43,7 @@ We need to move the ball half-width left and half-height up to make it center.
 So the final `left` would be:
 
 ```js
-let left = event.clientX - fieldInnerCoords.left - field.clientLeft - ball.offsetWidth/2;
+let left = event.clientX - fieldCoords.left - field.clientLeft - ball.offsetWidth/2;
 ```
 
 The vertical coordinate is calculated using the same logic.