This is not Nim.
From what I could discern: This is a human vs human game. Enter a number to start, and each player takes turns subtracting 1-3 only it seems. Which ever player is the last to subtract 3 or less, wins.
Strategy would be to present the player to lose with the number 4. To which they can only subtract 1, 2, or 3 from, and the next player will be able to take what is left.

For more info look it up:

From wikipedia:
"Nim is a mathematical game of strategy in which two players take turns removing objects from distinct heaps. On each turn, a player must remove at least one object, and may remove any number of objects provided they all come from the same heap. The goal of the game is to avoid being the player who must remove the last object."

"Nim is typically played as a misère game, in which the player to take the last object loses. Nim can also be played as a normal play game, where the player taking the last object wins. This is called normal play because the last move is a winning move in most games; Nim is usually played so that the last move loses."

Don't tell people to 'look up' how to play your game, especially if you use rules that are contrary to the way the game is usually played. How long does it take to write something out? Maybe a minute? Your game also lacks groups of items which in my opinion is an important part of the strategy in the game. This game has zero graphics the gameplay is lame at best, and the window seems to need to be reloaded to restart.

i don't even know how to play O_0