************ Introduction ************ Sensors are the logic bricks that cause the logic to do anything. Sensors give an output when something happens, e.g. a trigger event such as a collision between two objects, a key pressed on the keyboard, or a timer for a timed event going off. When a sensor is triggered, a positive pulse is sent to all controllers that are linked to it. The logic blocks for all types of sensor may be constructed and changed using the :doc:`Logic Editor ` details of this process are given in the :doc:`Sensor Editing ` page. The following types of sensor are currently available: :doc:`Actuator ` Detects when a particular actuator receives an activation pulse. :doc:`Always ` Gives a continuous output signal at regular intervals. :doc:`Collision ` Detects collisions between objects or materials. :doc:`Delay ` Delays output by a specified number of logic ticks. :doc:`Joystick ` Detects movement of specified joystick controls. :doc:`Keyboard ` Detects keyboard input. :doc:`Message ` Detects either text messages or property values :doc:`Mouse ` Detects mouse events. :doc:`Near ` Detects objects that move to within a specific distance of themselves. :doc:`Property ` Detects changes in the properties of its owner object. :doc:`Radar ` Detects objects that move to within a specific distance of themselves, within an angle from an axis. :doc:`Random ` Generates random pulses. :doc:`Ray ` Shoots a ray in the direction of an axis and detects hits.