To quote the description on Nintendo eShop:
"SteamWorld Dig is a platform mining adventure. Take the role as Rusty, a lone mining steambot, as he arrive to an old mining town in great need. Dig your way through the old earth, gaining riches while uncovering the ancient threat that lurks below...
Carve a path through the earth, and explore a deep underground world full of secrets, treasure, and terrors.
Uncover the remnants of Human civilization, a degenerate race of dynamite-wielding troglodytes.
Meet the weird and interesting townsfolk of Tumbleton and help the community get back on its feet.
Beautiful, high-res graphics with dynamic lights and multiple parallaxed background layers."
Okay, aside from some grammatical errors, that description sounds promising, and the trailer makes this game look pretty awesome! One comment on YouTube said it's like a better version of Terraria (thought he followed that up by saying Terraria was pretty terrible, so I don't know what to make of that...).
It currently costs $8.99 right now on the Nintendo eShop. I'm going to get it soon (it would be nice if I was informed about sales on this and the Wii U's eShop, if anyone can tell me how I can be informed about that kind of thing).