GOG Summer Sale 2016 begins - The Witcher 3, Rebel Galaxy, Day of the Tentacle, more

GOG's Summer Sale has officially begun.

GOG has officially kicked off this year's Summer Sale. The sale is live now and for the next two weeks. Over 1000 deals will be made available during, for up to 90 percent off.

To kick things off, GOG will give a free copy of System Shock 2 to anyone who downloads the store's Galaxy app during the first 48 hours of the sale. GOG wants to improve the client by using this giveaway as an opportunity to stress test it.

All you have to do to get the free game is visit the sale through the client itself.

The sale also has a form of meta-game, similar to the way Steam has done things in the past. Buying games and participating in daily activities earns you XP, which you can use to earn free games. These include Spelunky, Gabriel Knight: Sins of the Fathers – 20th Anniversary Edition, and Dreamfall Chapters Season Pass.

The site will also host Twitch streams designed to boost everyone's XP gain. The first starts Thursday, June at 4pm GMT. Stardew Valley and Grim Fandango Remastered will be the games livestreamed.

Deals change every 24 hours. The Witcher 3: Wild Hunt, Rebel Galaxy, Day of the Tentacle Remastered will be among the first few titles to go on sale.

Everything wraps up on Wednesday, June 22 at 1pm GMT / 3pm CEST / 6am PDT / 9am EDT.