One rule builds the whole pyramid
Start with two neighbouring stones. Add them, then write their sum in the stone directly above. The same rule works at every step of the pyramid.
Find the useful clue first
Some pyramids ask for an upper stone, while others leave a lower stone empty. Look at the nearby completed stones, decide which addition fact connects them, and fill in one missing value at a time.
The available interactive practice keeps every value between 0 and 20.