Glider guns were the most straightforward; they were oscillating configurations which continually generated gliders, solving one of Conway's questions: Is there a Life configuration for which the number of live cells can be demonstrated to increase without limit? They also make good Life demonstrations. A glider gun is a little larger than is convenient to illustrate here, but the principle behind it is not too hard to describe.
In addition to the period 30 oscillator shown in Figure 
,
there is another of period 46 which has been discovered, both of which
involve a central seed which expands into a cloud which just happens to
leave behind a copy of the original seed facing in the opposite
direction. Naturally this tends to repeat the cycle except for the
interference caused by the remaining products of the evolution.
It is at this point that placing stable elements nearby helps to create an oscillator; but if two oscillators are placed side to side, for the period 30 oscillator, or at right angles, for the period 46 oscillator, the debris may interact to produce a glider. For all this to work it is evidently important that the glider be small, and that small objects be of frequent occurrence. Even so, careful adjustment is required, and at that only one or two relative positions results in gliders which can break free.