This year's US presidential election could come down to results in just a few key states.
Most states are tipped to vote one way or another - so we have already assigned 188 votes to Mr Trump and 233 to Mr Biden.
Can Joe Biden wrestle enough away to seize the presidency? Or will Donald Trump romp home to a second term?
It's all about the race to 270 electoral votes - and this time you decide.
How did we pick these states?
In the US election system, it's the state-level results that count. Each state has a number of electoral votes, based on population, and many reliably vote the same way each time.
Two independent American sources, Real Clear Politics and The Cook Political Report, publish lists of states grouped by how they are expected to vote on election night. Several states are classified as "toss-ups", which means they could be won by either side.
We chose our seven key states from those toss-ups which have enough electoral votes to sway the final outcome and where we expect the battle to be fought most closely. President Trump won all of them in 2016
Why do the candidates start with some votes?
Since most states are already tipped to vote one way or another, we've assigned their respective electoral votes to the candidate that each is considered most likely to vote for. This means the game starts at 188 votes for Mr Trump and 233 for Mr Biden.
Can there be a tie?
Technically, yes. There are a total of 538 electoral college votes and it is possible for two candidates to win states in such a way that each will come out with 269 votes. Awkward.
It's also possible for no candidate to receive a majority.
To determine a single winner, the US House of Representatives will vote for the next president and the US Senate will vote for the next vice-president.
This is so rare, though, that it's only happened a few times in US history… and not since the 19th Century.
Written and produced by Harriet Agerholm, Becky Dale, Evisa Terziu and Sean Willmott
What questions do you have about the US election?
The US election process can be confusing. The BBC is here to help make sense of it. Please put your questions below.
If you can't see the form, you may need to view the site on a desktop.