In your (3 stepper vidar):

Eliminating 9 From r4c9 (Naked Single in Column 9)

Eliminating 4 From r4c9 (Naked Single in Row 4)

Eliminating 2 From r4c9 (Naked Single in Row 4)

Eliminating 7 From r4c9 (Naked Single in Box 6)

Eliminating 5 From r4c9 (Naked Single in Box 6)

Eliminating 6 From r4c9 (Naked Single in Box 6)

r4c9 value MUST be 1 (Hidden Single in Row 4)

r4c9 can only be uncovered as a hidden single........

if you looked at the board at the start you can't deduce that.......

If you place hidden singles AFTER naked singles then you are right, but clearly hidden singles are easier to spot than naked singles...

Naked singles uncovered by hidden singles are in the same step

Hidden singles uncovered by naked singles are in the next step

so r4c9 has to be in step 2 (out of 4

), that is how I see it.....

Tarek