You play as Skye, and you have to protect the core from strange alien creatures who don’t like your core-e ways. Starting off in the building phase, you prepare for the attack by placing various blocks and ‘towers’ to stop the aliens before they reach the core.
After the recent update allowing up to 4-player co-op, in Sanctum there is 5 maps, one that is exclusive to Endless mode and three which you have to unlock by simply playing the game. Difficulty ranges from “Easy” to “Insane” and the aforementioned ‘Endless mode’ does exactly what it says; you play until you die, rather than up to 25 waves in the regular mode. On top of that, you can also use “Turbo” mode which basically gives you everything from wave 1, which means the enemies are more difficult from the outset, too, as they get progressively more difficult in every game mode.
What makes Sanctum interesting is that it’s an FPS (First-Person Shooter) tower defense game. To build towers, you run around the map placing the blocks and then place the weapons inside/on them blocks, and then you can upgrade them up to level 6. To make things a little simpler, you can bring up a tactical map by pressing TAB which shows you where enemies spawn (where they are, if the wave has begun), where the core is, and you can also quick-travel to various televators you have placed on the map.
And, by the way, televators are a kind of tower you can build (or are already set if you’re playing on Mine), these work as teleporters as well as elevators (or ‘lifts’) for getting on top of your towers for a vantage point.
When everyone has hit Enter (to indicate they’re ready), the wave begins, and everyone drops their pink remote from their robotic hand and gets out their guns. You have an Assault gun, Sniper, and Freeze Gun, all doing their respective amount of damage, and shots/sec. The weapons are all upgradable – also to level 6 – and have alternate fire modes, e.g. the assault gun has a grenade attachment.
At the moment, you can easily kill a good several hours playing the few maps that are currently available, but the developers are working on extra content. And if you’re the type, there are lots of leaderboards for all the kinds of game modes including separate ones for single-player and multi-player, endless and turbo, etc and etc.
In conclusion, Sanctum is kinda fun on your own, you can have lots of fun with friends (like most co-ops), and you can even try to get on the leaderboards. You can get it on STEAM for a reasonable £9.99.