It can be stressful deciding what toy to buy for kids at Christmas.
Imagine, then, deciding what toys to buy to fill the shelves of Hamleys on London's Regent Street, where more than 650,000 shoppers have already walked through the doors this December.
It is a mammoth task that starts at the beginning of the year, according to Sumeet Yadav, who runs the retail business of Reliance Brands, which owns Hamleys.
He says the stores' buyers visit toy fairs all over the world to decide what children will want for Christmas, when Hamleys makes about a fifth of its money.
It's "a bit of science and a bit of luck", Mr Yadav says, describing their process.
The science is identifying and matching social trends with the toys being made by manufacturers.
This year, a lot of people are trying to spend more time with family in what Mr Yadav describes as a "disconnected world".
He suggests that explains the popularity of Pictionary Air, a digital twist on the old card game in which players have to illustrate a word or phrase on a card for their team to guess.
'Sometimes you go wrong'
"A lot of toys, which were traditional in the past, are now coming back with a technology connect," he explains.
As for the luck, Mr Yadav says: "Sometimes you go wrong."
The next challenge is to get those toys into the hands of children.
That starts with elves "creating a ruckus" on Regent Street, home to Hamleys' flagship store.