If I have the right answer, and that is a big if, the code has already been taken. Thanks for donating the code but can't say I learned much about "a lattice basis reduction algorithm".

Even easier, GOG = 4 groups of 4 characters, Steam = 3 groups of 5 characters.

The 39 Steps STEAM Y6F5Q-XPVCW-593483

A hex on the person that wrote down the last group of 5 characters!

Uh...I was just checking if I took the hint right and...thank you, I redeemed it :)

STALKER: Shadow of Chernobyl (Steam)
A&VF&-&EE!!-8QVJB
&&&=Digital Television.
!!=personal computer released in 1982.

Tried it, but says invalid code. Thanks for sharing!
EDIT: Ah, it was ZX, I was trying 64. :D Was taken already tho.

Melissa K. and the Heart of Gold (steam) 3QRH3-VJBG7-3W##C
Its just a double A game, not a triple A game

Frozen Hearth (steam) 8YEYW-DPTNC-2Z0##
unit for 1000 watt seconds

Melisa K. has already been redeemed by someone else.
Thank you blarth anyhow.

Ethan: Meteor Hunter (steam) 7###C-RL45N-M5BR9

Microsoft browser introduced in the last half of 1996.

Thanks, blarth! Have a nice day. :) Oh! And thanks for a Melissa K. game. It was me, but I was too sleepy to say "thank you" yesterday. I'm sorry.

CO-OP : Decrypted

###JP-GX7DL-2ZF2J

Got it, thank you!
It's not the same if there are no prime numbers involved :)

Incandescent

!!RCR-X@@DF-###N2

5919643

59, 19, and 643 are prime, but those arent't the primes you need. : )

I got it. You put lots of efforts to create some puzzles to trick the robots.
Thank you.

Akane the Kunoichi Steam Key: 2W9PY-QQ0PF-V###H


502 written using a different numeration system.