Instant Dungeon! is 15% off from May 11 - 14 to celebrate its newly added features; Steam Trading Cards and Steam Achievements.
Steam Achievements:
There are 51 achievements, you can view them from the Steam client or by selecting "Achievements" from the options or pause menu in-game.
You can see the achievements here:
http://steamcommunity.com/stats/326720/achievements
Steam Trading Cards:
You can now grab 5 trading cards each is an original composition by the artist Lukasz Jastrzebski. There are also 5 profile backgrounds and 5 emoticons which you will be able to collect randomly by crafting badges.