One of my favorite games ever, from one of my favorite devs is on sale! Grab it while it's hot! Or you can wait and buy it for full price to support him! Just sayin'.
This has been out since 2013 and this is only the second time it's gone on sale. If you've been on the fence, Now's the time to buy it. I've only been playing 15 minutes and I love it and can tell it's going to be on my device for years alongside Hoplite and Dungeon Raid.
I had my doubts about it dropping again, despite Michael Brough remaining semi-active in the TA Forums (i.e., not a Dungeon Raid situation). Anyhow, absolutely recommended if you like puzzle rougelikes -- The Nightmare Cooperative and Brough's own Zaga 33 being two that are similar, although 868-Hack has more things to consider than either.