Smart Moves

To get 3000 gamer score and unlock all achievements in this game all you need to do is open 50 chests and kill 50 snakes total. Replaying levels does count so you can milk one of the early easy levels if you like. Find an easy level and kill the snakes and open all but one chest, or leave a snake alive. Then hit the "Y" button to reload the map, rinse and repeat. Once you beat a level it does not seem to let you go back and replay it. Correct me if I am wrong please, input welcome.

Very simple, still killing snakes...

The best way I found to get quick snake kills is to go level 2 of the main game and then press and then repeat that over and over again.

For those past level 2 simply press + to reset your game data.

For those not yet at level 2 simply move your character around on level 1 to where your character is touching each of the 3 chests and that will beat level 1 for you. :)