Squash star Annie Au Wing-chi is often doing calculations - both on and off court. She is famous for knowing when to cleverly change the pace of a match or select a different type of shot to win a point.
Now she has begun doing sums of a different kind - adding up her average ranking points gained from tournaments - after she became the first Hong Kong-born player to break into the top-10 rankings in women's squash this month.
'People have the misconception that my ranking will only go up from now on - not drop down - but that's not the case,' says Annie, 22. She is ranked ninth in the world on 774.810 points - only just ahead of France's 10th-ranked Camile Serme, on 773.194 points.
'Nearly all the top players are really close to each other in terms of ranking points. That is why I'm always pressing the buttons of my calculator to see how my ranking will change if I reach a certain round. I just want to make sure my ranking won't fluctuate.'
Last year, Annie was ranked outside the world top 20 and not playing particularly well. But then last month she unexpectedly won an international tournament in Kuwait.
That victory proved the turning point - it inspired her to a second successive international title in France the same month and other impressive performances as she climbed the world rankings.
Being consistent is the secret to staying in the top 10, but Annie enjoys the added pressure this brings. 'If I've won a title the previous year, I will need to do equally well this year to defend my title. And if I performed badly last time, I know it is a good chance to improve and also grab more ranking points.'
Annie is aware that the world's top players are bunched close together in terms of ranking points. Two players, ranked 11th and 12th in the world, are only about 40 points behind her, while most of the eight players in front of her are more than 400 points ahead.
The exception is Annie's heroine, Nicol David, 27, of Malaysia, the world's number one player and world champion for the past three years. She is far ahead of everyone else; she has 3,348.750 points, while world number two Jenny Duncalf, of England, has 1,654.706 points.
'Nicol is my idol. She really is the toughest player I have ever seen,' says Annie. 'She hits the ball hard and moves as fast as a male player on court.
'It is hard to believe she is so far ahead of everyone else. That means she manages to produce consistently outstanding performances in all the major competitions.' Annie's unexpected success led her to delay taking the final year of her bachelor's degree in business administration at Hong Kong Polytechnic University this summer.
'My coach and I knew that I would get better results at last November's Asian Games in Guangzhou if I deferred my studies,' Annie says.
Her decision was vindicated when she won two silver medals. She lost to David in the women's singles final and again in the women's team final as Hong Kong lost out to Malaysia.
Annie still studies during her mid-day break, away from her daily training regime of running, weights and gym, and plans to graduate this time next year.
Her dream, apart from continuing to improve as a player, is to see squash become an Olympic sport. 'We were in the final two sports pushing for selection at the 2016 Olympics, but we lost out to golf,' Annie says.
'We need more support from the public and television coverage if we are to succeed. My wish is that the sport will be included in the 2020 Olympics, although by then I may be too old to play.'