The idea behind the PBP system is that players can gather activity points (called PBPs here, but they are nothing else than good ol' PAL points), and later trade these points for ships. This system is similar, but not identical, to the system implemented in HOST.
When this system is used, players must decide which ships are important to them, and mark these as priority builds. This is done by giving the associated starbase a PBn friendly code. Each player can designate up to 9 priority builds this way (because there are nine PBn fcodes. If you use one code twice, only one of them is accepted, so don't do that). PB1 is most important, PB2 second-most, etc. Unlike in the other build queue modes, you must keep the PBn codes on your bases until your ship was built.
Every turn, the first free ship slots are given to players ready to pay for it using their priority points. The player with most PBPs gets the first slot, until all slots are used up, or until no more priority builds exist. All ships built during this phase will cost priority points. If a player is granted a priority build but has not designated one, or he has not enough points to build his highest-priority ship, he is skipped.
If some ship slots still remain after all possible priority builds are processed, ships are built in FIFO order, oldest build order first.
