Magic: The Gathering is a collectible card game for 2 or more players, set in a variety of fantastical realms. The cards represent the player's resources and available spells and their interactions lead to an often high paced battle of wits.
So imagine this:
My 5/5 with trample attacks.
It's blocked by a 1/1 and a 2/2.
I assign damage as 1 to the 1/1, 2 to the 2/2, and 2 to the player.
And then they play a card to boost their 1/1, making ...