Free GOG Game: Worms Forts - Under Siege

1. Go here
2. Select the game and click Checkout Now
3. Login or Register your account
4. The game should automatically be put into your GOG library
5. Check your e-mail to verify you got the game

Bonus:

G2A: Prices Cut In Peaces Sale - 3% off voucher: KINGS

20% off voucher on most titles including Fallout 4, Just Cause 3, XCOM 2 & more