[~FREE] HumbleBundle's Spring Sale Encore Rewards (including Fortified)

You might remember Humble's Indie Mega Week Promotion.
It is back for the currently running Spring Sale.

Instructions:
You visit the store page to collect a stamp.
You claim your rewards here.
And will find your prices either here or here.

You get:

This week's Mission ends on May 24th at 10am PDT. Your stamps will not carry over, so act fast!.

Week 1 is running until May 17th at 10AM PDT. - Over
Week 2 is running until May 24th at 10am PDT. - Over
Week 3 is running until May 28th at 10am PDT.

Edit, a better guide on how to get your stamps from AquilaSol - credit goes to him/her, I copied it from here - thank you!

The claim button unlocks the reward. The name is a bit misleading, you don't trade stamps for rewards. Claiming a game does not remove that amount of stamps.

So once you get 1 stamp, you can unlock the voucher.
When you collect 2 more stamps, and have collected 3 in total, you can unlock the first game.
When you collect 2 more after that, and have collected 5 in total, you can unlock the second game.

You get stamps for clicking on the sale banner at the top of the Store page, and for every $5 you spend in the store. If you're not sure where to click, just click on the stamp image at the top of the store. If you can't see it, make sure you turn off your adblocker. (Some mistake it for an ad.)

(I had to physically click on the banner, the stamps didn't get added by itself from just visiting the page.)

The first set of stamps can be collected in the first week of the sale, so there are 7 chances to earn stamps via daily visits. If you miss a day, you can still get the games. (Missing a day does not cost you any previously collected stamps.)

You can view your progress and claim the unlocks on the Mission page. You can access this by clicking on your email/name at the top right, and clicking on Missions.

This week's Mission ends on May 17th at 10am PDT, at which time a new Mission will be enabled for the second week of the Spring Sale. Your stamps will not carry over and a new set of rewards will be available.

Make sure you claim all first-week rewards BEFORE the first third mission ends on 28 May 10AM PDT. The page and all collected stamps will reset at that moment, and you can not go back and unlock the first third week's rewards after that. (claimed rewards will be in your library.)
For all other timezones, here's a conversion of that time to all local times on TimeandDate.com.
And here's a countdown.