Game 21

Hardware requirement: Amazon Echo

Game 21 is a simple math game for 2 players. Alexa is one of the players.

Player 1 starts with a number from 1, 2 or 3.
Player 2 then can say any number from the 3 numbers following the number said by player 1. The game continues like this and the one who says 21 loses.

Example:
Player 1: 2
Player 2: 5 (valid numbers are 3, 4 and 5)
Player 1: 8 (valid numbers are 6, 7 and 8)
Player 2: 10 (valid numbers are 9, 10 and 11)
.
.
.
Player 1: 20
Player 2: 21 (Player 2 looses)