The rules are simple; you take the word above you and are allowed to change it in four ways. You can swap a letter for another (birds → bards), add a letter (word → sword), remove a letter (shimmer → simmer) or change a letter's place (deserts → dessert). You are also allowed to make up to three changes using any combination of changes you like (raptor → report → deportee → departed → retarded). As a tip: type the word in the reply box and edit it there.
And the starting word is…
angel