You're a Google snake, and you're crawling around endlessly trying to eat food while staying away from walls and your own ever-expanding tail in almost all versions of this game and believe me, there are a lot of things that work on the same principle, and the only thing that's advanced is the graphics and controls, nothing more. But I'm getting ahead of myself here.
Let's go back to the beginning. Your goal in the game is to maneuver the snake to eat the red apple.
As the level progresses, the difficulty will rise, so you'll need to move quickly to avoid the snake colliding with the obstacles.