NumberPairs app for iPhone and iPad

There are four numbers.
Number will vary depending on when any one tap "situation".
By changing the numbers is a game that will make more pairs.

area the numbers to change is a natural number of 1~20 (※).
You can ended up outside the area 1-2, what it no longer is a natural number in 5 ÷ 4 numbers will be reduced remaining turn-only does not change.

If the pair is able to enter one point.
Continuous to make a pair with and enter 2 points.
The remaining turn does not reduce when it comes to the pair.

Number that is tapped when it comes to pair changes to the same numerical value as the "rest turn".
The changes in "random" if further paired in the same turn continuously.

※Caution
Range that changes at random when it exceeds the "1-20" But the point is 20, the upper limit will be the same number as that point.
For example, a range that varies randomly when it becomes 21 point will be "1 to 21".