it's just a sliding puzzle
The bit that does make it a tad evil is that the empty space is in the middle which does rather break the standard solve method for sliding puzzles that relies on empty space being bottom right.
I solved it like it was a sliding puzzle and it didn't work.
I'm guessing you just got all the right shapes in all the right places - you need to pay attention to the colours as well. The 4 colours each move through 1 pipe to the middle square, so although several pipes are identical shapes they are unique pieces.
The pipes have to be the right shape AND the colours flow through them logically without jumping around.
Plus that last little factor of empty space being in middle makes last few tiles a pita to get right.