First giveaway

I found Steamgifts back in February and, since then, I've wanted to do something for you to solve. So here it is:

abcde fgioh uaeij kolum anepi qouae riost vuwax

The game is Half Life 2. A gift, not a key, so I'll add the winner in Steam.

Edit: I guess you already know it but you are looking for a 5 letters/numbers code.

Edit 2: I wrote some hints in comments if you are stuck.

Edit 3: forgot to say: the giveaway finish in April 17th, so you've got plenty of time.