You play this game by clicking on the gingerbread man, therefore you will be rewarded with gift-points which you can invest in buying gifts and upgrades to get more giftpoints per second or increase your maximum available gift-points.
That's a pretty simple clicker game, with no known limit.

you don't have to play the game to get all achievements.
Just push every single letter- and number- as well as the enter-, space- and escape-key on your keyboard.
That's it, 100% achievements.

You can alt+tab out of the game to check your progress in the game stats.

Ho ho hope this helps.