A reflex game of simple speed math. Play solo or local versus.

Best played fullscreen on a tablet, smartphone, or touchscreen PC.

How to Play

Solo

Choose whether each math expression's result is odd or even before time runs out. The time limit decreases gradually as the game progresses.

Keyboard controls are available in this mode.

ZOdd
XEven
SpaceRestart

Versus

There are 2 teams, Odd and Even. Each math expression's result has a parity of either odd or even.

There are 2 buttons in the center, ◯ and ✕. If the parity matches your team, press ◯. If it doesn't match your team, press ✕. Race against your opponent to press the correct button for your team.

Math Tips

It is not necessary to actually evaluate the expression to find out its parity. These are the rules of parity:

Addition and subtraction

  • even ± even = even
  • even ± odd = odd
  • odd ± odd = even

Multiplication

  • even × even = even
  • even × odd = even
  • odd × odd = odd

Easy and normal difficulties only include addition and subtraction, so determining parity in those difficulties is only a matter of counting the number of odd numbers. If there are an odd number of odd numbers, the result is odd.

Hard difficulty adds multiplication to the mix, forcing players to pay attention to the order of operations.

More information