About Odds and Evens
Odds and Evens is a finger game that was played in ancient Rome, and it is still used around the world to settle small disputes. Two people each show some fingers. The total is odd or it is even. That is all.
How a match works
At the start of each round, the screen tells each player whether they are Odd or Even. The roles swap after every round, so neither side has a lasting advantage.
Each player taps a number from one to five on their own side. The choice is hidden until both are in. Then the two numbers and their sum are displayed. If the sum is odd, the Odd player scores a point. If even, the Even player does. The first to five points wins.
Sitting and setting up
Lay the device flat between you. On a computer, player one uses the keys 1 to 5. Player two uses 6, 7, 8, 9 and 0, which stand for 1 to 5 in the same order.
What actually matters
Only one thing about your number matters: whether it is odd or even. An odd number plus an odd number is even. Even plus even is even. One of each gives odd.
So the Even player wants to match their opponent's kind of number, and the Odd player wants to differ from it. It is a guessing game about a single yes-or-no choice.
Notice that the buttons are not balanced. Three of the five numbers, 1, 3 and 5, are odd, and only two are even. A player who picks without thinking will choose an odd number more often than not. If your opponent seems to be tapping at random, the Even player should lean towards odd numbers, and the Odd player towards even ones.
Against a thoughtful opponent, look for their habits and hide your own.
It is quick, fair and older than almost any other pastime turned into HTML5 games.