Lock's Quest is a real-time strategy game, incorporating tower defense gameplay elements. The battlefield, viewed from an isometric perspective, is displayed on the DS's lower screen. The upper screen shows an overall map with locations of defences and enemies, as well as the remaining time in the battle.[1]
Combat is divided into two phases, Build and Battle. During the Build phase, the player has a limited amount of time and resources to construct defences, which consist of walls, towers, cannons, machines, and traps. Gates also allow Lock to move through defensive walls. Constructing defences consumes Source, which Lock can regain by defeating enemies.
The Battle phase follows the Build phase, and involves fighting waves of enemies while maintaining defences. Lock is able to attack enemies, and perform quick time events to deal additional damage. The player can also use Lock to repair damage done to defences, which requires another quick time event called "ratcheting".[2][3][4] The objective for most levels is to protect a particular individual or object. Enemies spawn in zones on the edge of the map and travel towards the target, attacking defences in their way.[5] On some levels, special "boss" enemies appear that must be defeated to end the battle.[2]
Siege mode is an optional minigame which allows players to gain bonus Source for the main levels. This minigame is a 2D side-scrolling tower defense game.[6]
In addition to the main campaign, a multiplayer mode exists where players build defences as normal on separate maps, but also control what enemies are sent against the other player.[6]