TWENTY TWENTY

HOW TO PLAY
You play this game against the MathBot.
TARGET: To reach 20 first.
RULES: Either you or MathBot can start the game.
The game starts by choosing either 1 or 2.
Then the other player has to choose the next number.
The next number can only be the successor or successor+1.
One who reaches 20 first, wins the game.

 

ILLUSTRATION
Assuming you want to start the game, you can start by choosing either 1 or 2.
Suppose you have chosen 1.
Now, it's your oppenent's turn to choose the next number.
Your opponent MathBot can choose either successor or successor+1, that is, either 2 or 3.
Suppose MathBot chooses 3, then you have the choices to choose either 4 or 5, and so on.