Missiles have the same color as corresponding Players (e.g. P0=M0, P1=M1, ...) except when joined together as 5th player by setting Bit 4 of PRIOR/GPRIOR. Then they have the color of register 3 COLOR3/COLPF3.

TRIG3: only on 400 and 800 machines, else a copy of STRIG1. 0 when trigger pressed, 1 when trigger released

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