Have you got the lcd display to work at all yet? If not, I suggest you put your game sketch aside for now and find a simple test sketch to prove that you can get the LCD working. For example a sketch that simply writes "Hello World" or something to the LCD. This will confirm that you have the correct wiring, libraries and object constructor and that no files are missing.
Getting displays with i2c backpacks working can be a little tricky the first time. But once you have it, its easy to use in later projects and well worth it for the pins you save. You may need to make use of a sketch known as the "i2c guesser sketch". This is because there are a number of slightly different LCD backpacks out there which need to be configured slightly differently in the object constructor in your sketch. The object constructor is the line in the sketch like this one:
LiquidCrystal lcd(A4,A5,A3,10,11,12); //Define LCD pins
That is the constructor for a standard 6-pin LCD. The constructor for your display will be a little different and the guesser sketch will try the most common combinations for you until you see something readable appear on the LCD screen.