Centinal is a period-100shuttleoscillator that was found by Bill Gosper no earlier than 1973 and no later than 1987, being the first oscillator of this period to be discovered. It combines the mechanisms of the period 46 and period 54 shuttles. Its duopletspark is able to reflect gliders by 90 degrees, a property that Gosper used circa 1984 to construct a p1100 MWSS gun.[1]