I called this a "space tank", simply because it's not similar enough to any tank on earth :-) It looks for a light source, aims at it, goes to the proper distance and shoots its shell.
You have to tune it to a specific light source, because it measures the light intensity to extimate the distance. For the same reason, it works at its best in an almost dark room with just the target light switched on.
It employes three motors (2 for motion and 1 for the shooting mechanism), two touch sensors (bumpers) and one light sensor (localizer).
The "localizer" is the light gray structure on the top, that contains the light sensor. I built a sort of pipe (using three motor cylinder parts) to narrow the detection angle of the light sensor.
Here you can see the mechanism to manually adjust the elevation (bottom), and the motor-driven trigger (centre).
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