Thanks to all that have helped! OK. So mouse events are fixed, although I switched to click instead of mouseover for interface reasons.
docs.google.com/open
The problem now is that once an enemy reaches the castle the health bars do not update correctly.
When you run the game...
LEFT CLICK on the circles on the map to build towers.
RIGHT CLICK to destroy a tower.
All works fine until one enemy reaches the end.
I suppose the problem is in the destruction of the enemy and hp bar.
Thoughts?