This roguelike turns Terraria into a sci-fi tower defense game, and it's a steal at $5

gamesradar.com:

A new roguelike hybrid of tower defense and Terraria-style mining is garnering some serious buzz with Steam players, and at a $5 price tag Wall World is well worth checking out.

Wall World starts with a creative sci-fi hook: humanity lives in structures built into the side of an incomprehensibly massive wall, and you're one of the miners who digs into that wall in search of valuable resources. You pilot a big robo-spider up and down the wall, and when you reach a digging point, you can drill in and explore the mine in your space suit and jetpack.

After a quick play session, I'm already hooked. The game starts with minimal instructions, but it doesn't need them. You've got a big laser that can mine blocks, garnering resources that you can carry back to your robo-spider and turn in for upgrades. You have to get back to the robo-spider regularly both to drop off your resources - you have limited carrying capacity - and to defend your location from regularly-appearing waves of monsters.

This all creates a constant tension where you want to delve deeper into the mine to get more resources, but you have to be prepared to quickly get back to your spider in order to defend it. It's great fun even in the earliest stages, where the big boss wave that appears every 20 minutes will likely immediately bring your run to an end. You'll quickly get upgrades to the robospider's guns, and eventually you'll be able to build turrets and other defensive structures to help even the odds.

This might all sound pretty familiar if you've played Dome Keeper - in fact, if you're feeling uncharitable, you might call this a Dome Keeper clone. But Wall World has two notable advantages over the game that clearly inspired it: it's only $5 on Steam