Sanctum is a first-person shooter tower defense video game, developed by independent developer Coffee Stain Studios.
In Sanctum, players take on the role of Skye, an elite soldier sent out to protect her home town, Elysion One, from hordes of mysterious alien creatures. To be successful in the task, the player will have to defend a "core" on each level. To accomplish this, the player builds defensive structures, and assists their structures by fending off the enemies themselves.
The gameplay in Sanctum can be divided into the building phase and the extermination phase. In the building phase, the player builds structures on a pre-defined grid, using the 8 'towers' chosen at the start of the level. These towers include stationary weapons, teleporters for the player's use, and pads that affect enemies moving over them. The player can also upgrade any of the 3 weapons equipped at the start. Building and upgrading both cost points, which are gained when enemies are killed.
In the extermination phase, a wave of one or more enemy types moves across the level towards the core. With each enemy that reaches the core, the condition of the core degrades from 100%; when the condition reaches 0%, the game ends. Unlike most tower defense games, the player is allowed to move about the level during this phase and attack enemies with different weapon types, much like in a typical first-person shooter. Touching enemies will result in the player being knocked back, but no damage is done.
There are 10 types of enemies in the game, 3 of which are air-borne. Because certain towers are more effective against certain enemies, and only a select few towers affect flying enemies, the player must plan for all possibilities when building defenses. To aid the player in this, information about upcoming waves is shown in the pause menu, as well as descriptions of the various enemies, towers, and weapons.
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