You'll get so engrossed building castles and barricades that you'll almost forget about the monsters in survival RTS Cataclismo, out next week in Early Access

I don't think I've ever paused so much in a strategy game. Survival city builder tower defence RTS Cataclismo is going to be a game with a lot of Steam tags attached, but also tons of screenshots on social media of our elaborate player-made fortifications. Utilitarian ring walls of beefy stone, ramshackle holdfasts held together with rapidly splintering wood, or—and this is where you’ll be hitting Spacebar before embarking on a lengthy building session—intricate labyrinths of medieval barricades that would have the Minotaur thinking 'This is a bit much, actually.'

As we've previously discovered, Cataclismo—out July 22 in Early Access form—is a game about building settlements, and then defending them from waves of ghoul-like Horrors. The campaign follows Lady Iris of the Last City as she embarks on an expedition to learn the secrets of her magical powers, and the apocalyptic mist the Horrors spawn from, every night. 

The days have you gathering resources and placing pre-fab buildings in traditional RTS style, while dispatching units to scout your surroundings, and plopping beacons down to expand your territory. Where the game lets you get really creative is with its bulging toy box of Lego-like building blocks, as you have to construct all your defences manually, brick by brick.

Using your stockpiles of harvested wood and stone, you’ll build walls to protect your citadel, and for your units to stand on to attack the Horrors. Stone is costly but strong, becoming Toughened if you build it four blocks high, while wood is great for placeholder or more decorative elements. You’ll end up combining both, as you construct things like scaffolding so your units can reach their perches, and stone merlons at the top of walls to improve their range. But whatever makeshift or magnificent structures you end up with, their structural integrity—and their position on the battlefield—is all that matters when a horde of Horrors emerges from the mist.

Make a wall too thin and they'll practically burst through it. Too tall and your units might be out of range. Make your defences too centralised and they'll find an avenue you hadn’t thought of and (crucially) haven't defended against. There's a lovely tension between knowing what you need to build and what you can build, with the resources you have, and that’s where the creative solutions—AKA the bodges—come into play. 

The Horror

I forgot that Horrors could climb slopes. (It's not entirely my fault, as the background scenery can be difficult to read). And because of that, my quarry was torn to shreds. I don’t have nearly enough stone to build a new wall on its sorely exposed slope, so I just sort of extended my current wall round the hill a bit. You can do that in Cataclismo: make your walls look a bit odd, for tactical reasons, just as long as they obey the laws of physics. With granular building mechanics come more granular decisions (bodges), and any number of routes that your defences (and indeed the Horrors that are attacking them) can be taken down.

That's where the tower defence tag feels appropriate: the big-brain realisation that you can venture out from your stronghold to make outlier walls that will delay or divert the Horrors. The swarm seems to prefer a direct route, and who can blame them when collapsing structures will often take out not just your units but any Horrors standing underneath them. There are even fully fledged tower defence side missions that focus purely on this puzzle-like aspect, although with the sophisticated building mechanics, you’re doing more than simply plonking some turrets down.

It's easy to forget that Cataclismo is only in Early Access when the interface for building is so slick and user-friendly. Not only can you build defences when paused, and undo recent blocks with Ctrl+Z, but recycling them will give you all your materials back, instantly—all refreshing acknowledgements of the fact that mis-clicks happen often in building games.

There's an unfinished but enjoyable campaign mode that tells a minimalist story fairly well, not beating you over the head with backstory, but with voice-acting that feels oddly placeholder (though perhaps it is?). Of course, the campaign's main job is to teach you the mechanics, and in that way Cataclismo's is a success, with every mission introducing some new element, or focusing on a different ingredient in its genre stew. One mission you might be exploring a map, with just a few units and navigational obstacles to overcome, the next you’re managing and expanding an existing outpost. It's all building towards the endgame, of this version at least: endless mode and skirmish maps, which should be enough to keep you occupied for quite some time.

Endless space

Endless is essentially a roguelike mode that drops you into a randomly generated map—a terrifyingly open map, at that. I've generated several worlds in the one available biome and have been put off by the amount of open space, as this is fundamentally a game about making deals with your environment. All of the campaign maps, and both skirmish maps, are densely contoured with hills and forests, to provide plenty of natural defences, and suggest chokepoints and defensive locations, but it all feels a bit hodgepodge in endless mode. You can almost smell the procgen, as you try to survive endless waves while spending currency to unlock units and blocks. It's a neat idea, but the handcrafted skirmish maps are where it’s at.

There are only a couple in the game currently, but you can tell they've been made with a designer's hand—and it's these maps that will give Cataclismo its longevity. I've played around with the intuitive level editor, and I can’t wait to see what people will make with it, and how (hopefully) populous the Steam Workshop will become.

Is there enough here right now, to make Cataclismo a good buy in Early Access? Probably not if you want a satisfying campaign, as currently it's a journey that's varied and exciting but without an ending. There's no proper sandbox mode yet, either, although that's planned, along with the rest of the story, and additional biomes for skirmish maps and endless mode. But the building feels so good, and is so rich with possibilities, that I can't see it wearing thin any time soon.