Citadel

Citadel is a comparatively slow-paced shooter that emphasizes planning and
careful movement over fast reflexes.

On a planet that was thought to be uninhabited, an underground city complex
has been discovered. The player’s task is to explore this city with a remote-
controlled hoverdrone, called Monitor, while trying to avoid its automatic
defense systems.

Monitor is controlled from a top-down perspective and can only be moved into
four directions, holding down the fire-button enables it to shoot in eight
directions. There are various stationary and moving enemies that activate when
Monitor gets close enough and start shooting when it moves. Some can shoot in
four, others in eight directions, while others only try to ram the monitor or
attack with homing shots.

Pressing the fire-button twice and then holding it activates a capture probe
that can be used to pick up items, operate switches and control hostile
drones. Drones under Monitor’s control follow it around and can be used as a
shield against projectiles, a battering ram against other drones or a plug to
prevent more enemies from emerging from a trap. Captured movable drones
automatically move into the direction Monitor is firing in, but can also be
locked in a relative position by pressing the space bar. In order to be able
to capture a drone, a certain amount of energy is needed, depending on the
type of the drone. Items to replenish energy can be picked up as well as
better weapons like rapid-fire or two- or three-way fire.

There are eight cities to explore, each consisting of two floors connected via
lift shafts. Usually, reaching the exit of a city involves going back and
forth between both floors and deactivating various beam generators that block
the path.