yep, the surge is the darkest line then it very rapidly goes to no line. I was mucking around this cycle thinking I had already O'd but did one a week after I thought and the line was darker than the control line!! I couldn't believe it so an hour later when I went to pee again I checked again and this time it was lighter so I did a second brand and it was the same and by evening it was so faint I could hardly tell. I had O pains 11pm that night and the next day the OPKs were totally white.