to complete pairs, you have to match all of the 18 pairs of pictures by clicking on two of the boxes to reveal a picture under each one. if the pictures match, they stay up. but if they dont, then they will disappear again! you have to remember where the pictures were so if you find the other pair, you will know which two boxes to click on.
you win when all of the pairs have been found. the clock at the bottom will stop so you can see how fast you did it in and just above that, you will be told how well you did. a time of:
under 70 seconds is excellent
between 70 and 79 is good
between 80 and 89 is quite good
between 90 and 109 is ok
between 110 and 129 is quite bad
between 130 and 149 is bad
over 150 seconds is rubbish!