Adafruit_Arcada' does not name a type;
There are some instructions at:
Pygamer setup
That need to be followed in order to permit the Arduino IDE to work with the Pygamer.  It's not clear that you have followed any or all of these instructions.
I recommend that you carefully follow ALL the steps and then start with the simple example to test that you are building and uploading properly.
Then move on to the Adafruit example that uses the Arcada library.