save-restore.lua

function savePiecePositions()
    savedPieces = {}
    for _, obj in ipairs(getObjectsWithTag("Resettable")) do
        savedPieces[obj.getGUID()] = {
            data=obj.getData(),
            position=obj.getPosition(),
            rotation=obj.getRotation(),
        }
    end
end

function restorePiecePositions()
    for _, obj in ipairs(getObjectsWithTag("Resettable")) do
        local guid = obj.getGUID()
        local saved = savedPieces[guid]
        if saved == nil then
            -- Piece that wasn't around when we saved; delete it
            obj.destruct()
        else
            -- Put it back where it was, and un-save it
            obj.setPositionSmooth(saved.position)
            obj.setRotationSmooth(saved.rotation)
            savedPieces[guid] = nil
        end
    end
    for _, saved in pairs(savedPieces) do
        -- Any saved pieces we haven't yet restored were deleted; re-spawn them.
        spawnObjectData(saved)
    end
end