Have got most of the grid filled (1 ac being one of my last to get) - but still in difficulty parsing 33 - is the definition the first two words? FWIW my "shape" consists of rows of 3, 8, 10, 11 and 12 cells, with the 'start' and 'end' cells at (11,6) and (4,3) respectively. Also completely at sea with the '7 empty cells' endgame, as I am left with just two blanks in the second-last row! Where have I gone wrong? Any gentle nudges gratefully received!
For 11d I think the definition is the last 5 words of the clue, changing 'sides' in an illuminating technique.
For 10d the shifted letter creates a town in a country whose language is the answer.