Last April, Valve launched a guerrilla marketing effort for Portal 2 and promotion on select indie titles. This week Valve remembers its ARG campaign with the Potato Sack Reunion sale, which knocks half off the price of 13 individual indie titles.

Games include Super Meat Boy, The Ball, Cogs, Amnesia: The Dark Descent and many more. You can either buy each individually for half-off, or grab the whole bundle for $20.