MELBOURNE, Australia -- Roof open. Roof closed. Sunny, then overcast, then rain. Put your left hand in and you shake it all about.
Melbourne is infamous for having four seasons in a day -- just ask any Melburnian and they'll be happy to tell you -- but the effect that changes in the weather have on playing conditions, even on covered courts where there can be so many variables, can be drastic.
Under the roof, especially on warmer days, the courts are cool, and humidity plays its part in the action. On milder, perhaps wet days, the wind eases and the courts may warm up under cover. These changes have an impact on how the courts, balls and, ultimately, competitors play.
Players need to adjust their games accordingly -- quickly, on the fly and often without interference from their coaches box.
Throughout the first week of the Australian Open, Mother Nature threw a few curveballs the way of competitors, with howling winds making way to blazing sunshine, to sudden and heavy rain. And while the surface at Melbourne Park is considered a hard court, players still find conditions change depending on the weather as well as the time of day the match is played.
"[The conditions] change a lot," No. 4 seed Daniil Medvedev said after his second-round match against Pedro Martinez Portero, during which the roof of Margaret Court Arena had to be closed. "It was gray when we stepped out on the court, so we played just one game on, let's say, an outdoor court.
"As soon as the roof is closed, everything is different. It gets more hot, more humid inside. The ball goes faster too. I think the sound of the ball is different, so everything is completely different. I think on some days [weather changes] are to my advantage, sometimes it can be to your disadvantage."
While sudden and drastic changes in the weather and therefore court conditions can occur mid-match, Medvedev says when it boils down to it, conditions are also different from one match to another -- so many players are already used to needing to be flexible with their game plans.
He said when conditions change quickly, and the roof needs to close on Rod Laver or Margaret Court Arena for instance, the process of adjustment just needs to be sped up a little.
"It's like playing on Rod Laver or Court 3," he said. "It's going to be different so you have to adjust your match and try to win it."
Even a 20-time Grand Slam champion like Roger Federer pays close attention to the conditions in which he is set to play, at times going so far as to say he ignores tournament statistics as they may not be relevant for the next match.
"Statistics don't always mean everything," Federer said. "These conditions here in Melbourne, especially in the night time or under the roof where I've played twice now, you can start seeing the ball extremely clearly, as there's no wind, no [contrast between] shade and sun, and it does sometimes feel like clay court where you can maneuver your opponent around, and it's easier to construct a point.
"Whereas if it's faster [earlier in the day], you've got to hit in on the back foot. Sometimes you hit it late and hope it stays in."
But some players try not to overanalyse the changing conditions, instead choosing to focus on the strengths of their own game. 2016 Australian Open champion Angelique Kerber says the weather down under can be so unpredictable that it's not really worth considering.
"I mean, it's Melbourne, you never know what to expect," she said. "So I just try to focus on the game, playing how the game plan was drawn up, and I'm not normally worrying about the weather conditions."
Another variable players have had to adjust to is how different balls play on the court. For the past two tournaments in Melbourne, players have been using Dunlop balls, after the Australian Open ditched Wilson in 2019.
Federer believes these balls have a unique signature compared to their predecessors.
"Conditions play on the faster side when the balls are new," he said. "They get extremely slow when they fluff up."
Australian John Millman is in the same camp, explaining how the rapid deterioration of the balls leads to more longer, harder slogs.
"The courts are ripping up these balls and there aren't many free points to be had," he said earlier in the week. "There have been some extended rallies out there, and these best-of-five encounters are tough. It's physical tennis."
Millman isn't wrong. This year, through two rounds, there had been 24 five-set matches on the men's side of the draw, the most since 1998.
The peculiarities of the Dunlops also mean there are matches within matches, so to speak. For those who prefer a faster ball coming onto the racket, the first two or three games provide the best opportunity to force a break of serve, while for those who prefer a baseline-based defensive game, it's later in the balls' seven-game life cycle that suits them better.
However, some players aren't overly interested in the nuances the weather, ball or court conditions have on their game.
Rising Australian star Alexei Popyrin was asked if both the courts and balls were playing fast enough to suit his game at this year's tournament. The response was assured: "definitely."
"I don't think it matters what court you play on for my style of game," he said. "I think playing on any surface, any conditions, I'm just going to look to play my game. I'm not going to change my game at all.
"I'm always going to be aggressive, I'm always going to try to be on the front foot, come into the net and have the big serves."
For as many possibilities there are in the weather, variables on court and changes in the ball's behaviour, there are just as many opinions on how much they should factor into a player's match preparations.