This is showing easy ways to beat every single level in the expansion in hard with the hardcore option enabled and thereby achieving the Easy as Pie achievement.

Walk in the Park: "Complete the Goblin Menace expansion on hard using hardcore mode"

Note: You only have to beat the 7 expansion levels for this achievement. The original levels has a seperate achievement
To unlock level 7, you have to find all secrets. This can be done in easy without hardcore mode enabled though