I'm completely stuck - I've sussed that you can't walk on the sand (hands push you pack if you try) and I've made my way over rocks, fought everyone that pops up, smashed all the boxes and collected what's on them, and made my way along the spine of the big skeleton but when I reach the end of that, there's more sand. I can't work out where to go next. I've tried everything I can think of and I'm totally out of ideas. Help!!!