I failed at my favorite Steam Next Fest strategy game and its Lego-style building because monsters ate my stairs

I'm a known strategy-game turtler, which means that I'll spend as much time shooting arrows off the top of a great big stone wall as games like Age of Empires 4 will let me. That habit made me a big fan of 2017's They Are Billions, which condensed the RTS experience into a huge horde-defense mode, and now it's turned me towards Cataclismo, which might have the most promise of anything I've played so far in Steam Next Fest.

I've dabbled in a demo that feels relatively small as a result of the extent of its tutorialisation, but as the training wheels started to come off, I started to get a sense of just how Cataclismo would work. Each night, waves of mutated enemies known as Horrors will attack your settlements, throwing themselves mindlessly at your walls as they attempt to take down your Citadel, the central command center from which your bastion against this fallen world is run.

To stand against those Horrors, you can erect walls and train units to patrol them. But while a more traditional RTS might let you click and drag a huge stone monolith between you and your foes, Cataclismo lets you use each stone block like a Lego piece, placing it exactly where you want it to go. The higher you build your wall, the sturdier it will become, incentivising true bastions for your enemies to break themselves against.

It was a bit simplistic to start, but after my second wave, I started to get a better idea of where the strategy could really kick in. I could put my archers on top of huge wall, but if the Horrors dug a block out from underneath them, the entire structure would collapse, leaving my soldiers to tumble into the mass of foes beneath them. That led me to invest more closely into a warren of wooden balustrades behind my main wall, allowing archers to move more freely, taking full advantage of the buffs that came with getting an aerial advantage over the horrors.

As the final wave threatened me, I realised that I could use leftover resources to further corral the Horrors as they approached. I might have my main defensive wall, but I could place extra obstacles in my enemies' path to stall them for a few extra moments as my archers got in a few extra shots. It was hardly a genius strategy, but it was an interesting means of putting the game's Lego-esque toolset to work. I'm also sorry to say that it didn't really work, because I left all my archers on one wall, and once the Horrors took out the stairs up to that wall, my units couldn't get in range of the monsters that were chowing down on my citadel. A slightly ignominious end, but testament to just how intricate Cataclismo's building could be.

Outside of the building itself, there are a few interesting ideas tied up within the game's setting. I didn't really get a good impression of the internal mythology, but there was one bit of worldbuilding I enjoyed. Cataclismo's world is shrouded in Mist, and you'll need to pump out extra oxygen to fuel your settlement, using the gas as a resource to create buildings and train new uints. Oxygen purifiers produce more breathable air the higher they're placed, and they can be plonked right on top of pre-existing structures, so there's an interestingly cyclical format to creating new buildings to grant enough room to gather the oxygen you need.

All told, I think there's a lot of depth to Cataclismo that's yet to be shown off. It felt like I only had access to a pretty limited array of building and unit types, so I'm keen to see what a full-fledged settlement can look like once there are a few more toys to play with, and how robust that Lego-style building system will end up being. Due next summer from the team behind the excellent Moonlighter, and already nearly two-thirds funded after just a day on Kickstarter, it feels like this will be a fun one to keep an eye on.

Here's our selection of the best Steam Next Fest demos to play this week.