So, I loaded this up, annnnd.
just do ya know there are no pressure plates to activate the gravel/tnt so it dosent work
and you cant have multi level tnt run like this, i added A pressure plate and now there is a GIGANTIC hole in my world (no worries I put it in a new world so no read damage done) the water on the botem only protects that botem layer so the other levels cause a chain reaction of KABOOM.
THE ONLY REASON IM SAYING ALL OF THIS is because this page says you are 100% done, annnd, well its not. sorry if this sounds kinda harsh but hope this helps.