Fortnite is constantly doing crossovers, so the announcement that Epic had teamed up with Lego for a new survival mode glanced off my consciousness like the announcement of a new line of Funko Pops. But we just tried the mode, which has already attracted over two million concurrent players after launching today, and it’s way bigger and more fun than we anticipated—and, of course, free.

Survival games of this type are plentiful: It’s roughly the Minecraft setup, though without voxel digging. You punch trees, get wood, build crafting stations, make tools, build better things. At night, spiders and skeletons and other monsters attack. But rarely are new survival games this refined at launch. 

We’ve got quibbles, like that you can’t eat food directly from the inventory menu and creating even building surfaces is a challenge, but it’s intuitive and satisfying to run around beating up trees and building shacks so far. Combat is simple sword-and-board action with a block and dodge, but it’s fluid and responsive. Rocks have a nice crackle when you smack ’em with a pickaxe, and Fortnite’s impressive Unreal 5-powered lighting looks just as great when the sun is setting on plastic bricks.

I especially enjoyed the discovery that you can pick up giant boulders and hurl them around, inadvertently or intentionally knocking over your structures. It’s not Breath of the Wild level physics sandbox play, but our first impression is that there’s a lot more here than just a novelty mode that’ll be fun for a day.

Having only just started the game—and it does seem proper to refer to it as a game, not just a mode—we don’t know how deep the tech tree goes, or how big the generated worlds are. Checking in on Twitch, though, we’re seeing streamers in biomes we haven’t discovered yet, and they have better loot, too: shields, crossbows, and food that grants Zelda-like elemental resistances. We’ve found little surprises of our own; at one point Morgan wandered off in the direction of a rainbow fairy and was led to a treasure chest.

One surprising detail of Lego Fortnite you’ll encounter upfront is how robust and generous its server system is. You can spin up a server in seconds and invite friends to your world. By default, worlds aren’t persistent. Friends are considered “visitors” that can craft and build alongside you, but will leave the server if the hosts leaves and drop everything in their inventory. A world can become persistent if the world owner gives a friend a “world key.” Players with keys to a world can play on it even if the owner is offline. The owner can hand out up to seven keys, with a maximum of eight players possible on a server at once.

It’s similar to how Mojang handles its official Realms servers in Minecraft, but what’s wild is that Fortnite is letting millions of players set up persistent worlds completely for free. That instantly makes Lego Fortnite one of the most accommodating and accessible survival games around.

If you’re not a Fortnite player already, you can play Lego Fortnite by installing Fortnite on the Epic Games Store and then selecting Lego Fortnite from the main menu. One note: As a newcomer, you might wonder how to customize your character so that you don’t appear as whatever default you’re assigned. Fortnite’s kind of weird: your character’s appearance is defined by their outfit, so unless you have one that works in the Lego mode (there are apparently over 1,000 that do at launch), you’ll either have to accept the character it gives you or buy some V-bucks and pick up a new outfit.