Taken from facebook page:
FREE ORIGINAL 1997 CONSTRUCTOR GAME ON PC for all our fans. PLEASE LIKE OUR FACEBOOK PAGE.
The time has come. Here is the promo code and link to GOG to get your free copy of the original 1997 Constructor. on PC. Just click on the link and enter the promo code
Promo code code is: CNXZTWUC and it can be activated here https://www.gog.com/redeem.
The code will only work after 3pm CET time today and not before.
PLEASE DO NOT TRY TO DOWNLOAD BEFORE 3pm CET TIME AS YOUR CODE WILL NOT WORK. THE CODE IS VAILID FOR 24 HOURS ONLY AND EXPIRES AT 2.59pm TOMORROW FEBRUARY 1st
edit:Should be live 2pm UK time
edit direct URL https://www.gog.com/game/constructor
Live again for 48hrs (approx 1600 4/2/17)
Code - ZVSYRAFB