Sudoku is the fiendishly addictive number... to be good at Sudoku!
It looks stunning, and appears to be fiendishly clever.
WORKING out how much money you will have in retirement is fiendishly complicated.
About twenty kids, and a proportionate number of mothers were playing some fiendishly complicated party game on the grass.
elegance into fiendishly difficult puzzles... to solve a simple 4 x 4 Sudoku puzzle.